phosphocreatine and Coronary-Disease

In contrast to the established nuclear imaging techniques magnetic resonance imaging (MRI) is only in the early phase of its application to detect viable myocardium after myocardial infarction. Although MRI techniques have only recently been employed to assess residual myocardial viability three approaches have been described to achieve this purpose: First, the use of signal intensity changes on spin-echo images with and without the application of contrast media to define irreversible injury to the myocardium in acute and subacute infarcts; second, measurement of metabolite concentrations within the infarct area using magnetic resonance spectroscopy, and third quantitation of myocardial thickness and systolic wall thickening in chronic infarcts with and without positive inotropic stimulation. When applying magnetic resonance techniques to detect viable myocardium by imaging techniques, it is useful to distinguish between acute infarcts and chronic infarcts that are more than 16 weeks old. After the time, practically all infarcts have healed and the necrotic myocardium has been transformed into scar tissue. MRI seems ideally suited to detect and characterize chronic myocardial scar and distinguish it from viable but hibernating myocardium because it clearly depicts the regional wall thinning which is a typical feature of transmural infarcts (Figure 1). In contrast, more recent infarcts, even if they are transmural and fail to show any contraction during systole, may not yet exhibit myocardial thinning. Therefore, simply depicting the acutely injured myocardium by MRI is not sufficient to differentiate between necrotic and stunned, but viable myocardium. On the other hand, an increase in signal intensity of acutely infarcted myocardium, which appears on T2 weighted spin-echo MR images only a few hours after occlusion of a coronary artery, can be used to determine the extent of irreversible myocardial damage (Figure 2). It is not clear, however, whether this area of increased myocardial signal intensity that is seen within the first week after the event only represents necrotic myocardium or incorporates some edematous viable myocardium in the infarct border zone. After three weeks, true infarct size may be more closely approximated by the area of increased signal intensity because the edema surrounding the infarct has presumably regressed and signal abnormalities are restricted to the pathologically determined infarct area. More recently, new pulse sequence

Topics: Adenosine Triphosphate; Coronary Disease; Energy Metabolism; Heart Ventricles; Humans; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Myocardial Contraction; Myocardial Infarction; Myocardial Ischemia; Myocardium; Phosphocreatine; Ventricular Function, Left

Magnetic resonance spectroscopy (MRS) is a valuable tool for the study of myocardial ischemia. Phosphorus (31P) MRS can detect changes in high-energy phosphates resulting from ischemia and has been used to determine the sensitivity of metabolic changes to ischemia as well as to investigate the metabolic factors important for myocardial dysfunction. The mechanisms mediating postischemic dysfunction have been investigated using 31P MRS, as have interventions to limit metabolic and functional damage from ischemia. These investigations have laid the groundwork for human cardiac studies. While abnormalities following myocardial infarction have been shown in man, further work must be performed to reliably acquire localized spectra under conditions of ischemia.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Heart; Humans; Magnetic Resonance Spectroscopy; Myocardial Contraction; Phosphocreatine; Phosphorus

Topics: Adenosine Triphosphate; Animals; Biological Transport; Calcium; Coronary Disease; Electron Transport; Energy Metabolism; Humans; Hypoxia; Mitochondria, Heart; Myocardial Contraction; Myocardium; Phosphocreatine

The effects of 20th-century stress on the cardiovascular system are reviewed and correlated with experimental animal models. A classic example of such stress is drawn from a study of the aerospace workers at Cape Kennedy who were shown to be exposed to excessive occupational stress. Surprisingly, the usual risk factors did not predict a greater risk, yet the population exhibited a higher incidence of sudden cardiac death and acute myocardial infarction. Acute myocardial necrosis was much more frequently demonstrated than was acute coronary obstruction of any type. Retrospective coroner's studies revealed two types of myocardial necrosis: 1) elongated, thinned or wavy fibers and 2) anomalous contraction bands. Correlation of these clinical observations with experimental data was duplicated in canine models of myocardial infarcion and/or catecholamine-induced necrosis. Catecholamines can lead to irreversible myocardial necrosis but the underlying mechanisms appear to be complex. Extrapolation of the results from the experimental and clinical studies suggests that environmental stress can lead to myocardial necrosis.

Topics: Adenosine Triphosphate; Animals; Catecholamines; Coronary Circulation; Coronary Disease; Death, Sudden; Disease Models, Animal; Environment; Fear; Heart Arrest; Humans; Isoproterenol; Myocardial Infarction; Necrosis; Phosphocreatine; Stress, Psychological; Time Factors

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Anesthesia; Anesthetics; Animals; Blood Transfusion; Coronary Disease; Depression, Chemical; Dogs; Droperidol; Fentanyl; Heart; Hemodynamics; Lactates; Myocardium; Neuroleptanalgesia; Nitrous Oxide; Oxygen; Oxygen Consumption; Phosphocreatine; Shock, Hemorrhagic; Time Factors

Topics: Adenosine Triphosphatases; Adenosine Triphosphate; Animals; Calcium; Cardiomegaly; Coronary Disease; Digitalis Glycosides; Heart Failure; Hemodynamics; Humans; Myocardium; Myosins; Necrosis; Norepinephrine; Oxygen Consumption; Phosphocreatine; Propranolol

Topics: Adenosine Triphosphate; Animals; Cell Nucleus; Citrates; Coronary Disease; Disease Models, Animal; Dogs; Endoplasmic Reticulum; Glycogen; Heart Arrest; Hypothermia; Microscopy, Electron; Mitochondria, Muscle; Myocardium; Phosphates; Phosphocreatine; Potassium; Potassium Chloride; Procaine; Rats

Topics: Adenine Nucleotides; Aerobiosis; Anaerobiosis; Animals; Asphyxia; Cold Temperature; Coronary Disease; Dogs; Glycolysis; Heart Arrest; Homeostasis; Hypoxia; Ischemia; Myocardium; Oxygen Consumption; Phosphocreatine

After hospitalization for chest pain, women are more likely than men to have normal coronary-artery angiograms. In such women, myocardial ischemia in the absence of clinically significant coronary-artery obstruction has long been suspected. Most methods for the detection of the metabolic effects of myocardial ischemia are highly invasive. Phosphorus-31 nuclear magnetic resonance (31P-NMR) spectroscopy is a noninvasive technique that can directly measure high-energy phosphates in the myocardium and identify metabolic evidence of ischemia.. We enrolled 35 women who were hospitalized for chest pain but who had no angiographically significant coronary-artery obstructions and 12 age- and weight-matched control women with no evidence of heart disease. Myocardial high-energy phosphates were measured with 31P-NMR spectroscopy at 1.5 tesla before, during, and after isometric handgrip exercise at a level that was 30 percent of the maximal voluntary grip strength. We measured the change in the ratio of phosphocreatine to ATP during exercise.. Seven (20 percent) of the 35 women with chest pain and no angiographically significant stenosis had decreases in the phosphocreatine:ATP ratio during exercise that were more than 2 SD below the mean value in the control subjects without chest pain. There were no significant differences between the two groups with respect to hemodynamic variables at rest and during exercise, risk factors for ischemic heart disease, findings on magnetic resonance imaging and radionuclide perfusion studies of the heart, or changes in brachial flow during the infusion of acetylcholine.. Our results provide direct evidence of an abnormal metabolic response to handgrip exercise in at least some women with chest pain consistent with the occurrence of myocardial ischemia but no angiographically significant coronary stenoses. The most likely cause is microvascular coronary artery disease.

Topics: Adenosine Triphosphate; Adult; Aged; Case-Control Studies; Chest Pain; Coronary Angiography; Coronary Disease; Exercise; Exercise Test; Female; Humans; Magnetic Resonance Spectroscopy; Middle Aged; Myocardial Ischemia; Phosphocreatine; Phosphorus

Topics: Adenosine Triphosphate; Carnitine; Coronary Artery Bypass; Coronary Disease; Double-Blind Method; Heart; Humans; Myocardium; Phosphocreatine; Placebos; Stroke Volume

Topics: Angina Pectoris; Arrhythmias, Cardiac; Arteriosclerosis; Clinical Trials as Topic; Coronary Disease; Heart Failure; Humans; Injections, Intravenous; Myocardial Infarction; Phosphocreatine

Coronary angiography is still the gold standard for the diagnosis of cardiac allograft vasculopathy (CAV) for which alternative non-invasive diagnostic approaches are currently investigated. In this study, we assessed whether 31P magnetic resonance chemical shift imaging can diagnose CAV by studying variations in cardiac high-energy phosphates in a population of adult heart transplant recipients.. CAV was defined by coronary angiography as the presence of diffuse coronary irregularities with significant concentric narrowing on epicardial or distal coronary arteries. Eight patients with CAV (group A), and 18 patients without CAV (group B) were included in this study and compared to nine healthy volunteers (group C). Patients and volunteers underwent 31P three-dimensional chemical shift imaging to determine the ratio of phosphocreatine (PCr) and adenosine tri-phosphate (ATP). PCr/ATP was significantly lower in group A (1.51+/-0.50) than in groups B and C (1.98+/-0.53 (p=0.003) and 2.14+/-0.31 (p=0.001)), respectively. Time from transplant, number of episodes of acute rejection, and left ventricular ejection fraction (LVEF) were not significantly different between patient groups. A PCr/ATP value of 1.59 was the optimal cut-off value to predict CAV (specificity and sensitivity of 100% and 72%, respectively).. Clinically, in vivo 31P chemical shift imaging is a promising, non-invasive method to detect the potential modifications of high-energy phosphates related to CAV and to better screen indications for coronary angiograms. This may be relevant for coronary angiography follow-up and adjustments of immunotherapy regimen.

Topics: Adenosine Triphosphate; Adult; Coronary Disease; Coronary Vessels; Female; Graft Rejection; Heart Transplantation; Humans; Magnetic Resonance Spectroscopy; Male; Phosphates; Phosphocreatine; Phosphorus Isotopes; Stroke Volume; Time Factors

Experiments on dogs showed that energostim, a directly acting antihypoxant, injected 15 min after occlusion of the upper one-third of the left descending branch of the interventricular coronary artery produced a pronounced cardioprotective effect. The effect was confirmed by electron microscopy (evaluation the necrotic focus), biochemical tests of the heart and blood, and changes in intracardiac hemodynamics (recovery of systolic and diastolic functions). The cardioprotective effect of energostim greatly surpasses that of routine therapy applied during acute myocardium infarction.

Topics: Animals; Antioxidants; Coronary Disease; Coronary Vessels; Dogs; Heart Ventricles; Hemodynamics; Microscopy, Electron; Myocardial Infarction; Myocardial Ischemia; Myocardium; Necrosis; Phosphocreatine; Time Factors

To characterize energy metabolism in vivo after nontransmural anterior myocardial infarction, patients (group A, n = 19) with a stenosis of left anterior descending artery (LAD) and anterior wall hypokinesia by levocardiography were examined by phosphorus magnetic resonance spectroscopy (MRS). Spectra were compared to those of healthy volunteers (n = 15). The volume of interest was placed into the anterior myocardial wall by magnetic resonance imaging. Phosphorus spectra were recorded under optimal antiischemic medication. To separate the influence of coronary stenosis from that of the ischemic insult, additional patients (group B, n = 4) with LAD-stenosis but without left ventricular dysfunction were examined. The effect of antiischemic medication on the phosphorus spectra was evaluated in patient group C (n = 4), who had the same clinical features as group A. In these patients, MRS was first performed without antiischemic medication (washout period > one day) and then repeated during intravenous application of glyceroltrinitrate (GTN). Mean PCr/ATP-ratio was significantly lower in group A patients (1.24 +/- 0.18) than in healthy volunteers (1.74 +/- 0.23; p < 0.01 unpaired t-test). Patients with normal left ventricular function (group B) showed PCr/ATP-ratios (1.64 +/- 0.22) similar to those of normal controls (p = 0.23). After GTN infusion PCr/ATP-ratio of group C rose from 1.12 +/- 0.08 to 1.32 +/- 0.13 (p < 0.01 paired t-test). Thus, hypokinetic myocardium after nontransmural infarction is characterized by a larger decrease of the cellular energy buffer PCr compared to the myocardial ATP-content. These findings may reflect degenerative changes of myocytes due to disturbed microperfusion in viable areas of the infarct or remodeling processes of viable myocytes in the infarct region. Both mechanisms may lead to adaptive changes of cellular enzyme concentrations resulting in a reduced PCr content of the myocytes.

Topics: Adenosine Triphosphate; Adult; Aged; Coronary Disease; Diagnosis, Differential; Electrocardiography; Energy Metabolism; Female; Humans; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Male; Middle Aged; Myocardial Contraction; Myocardial Infarction; Myocardium; Nitroglycerin; Phosphocreatine; Signal Processing, Computer-Assisted; Vasodilator Agents

During moderate reductions of blood flow, the myocardium downregulates contractile function and ATP utilization to result in reduced but stable ATP levels, recovery or stability of (reduced) creatine phosphate (CP), and preservation of myocyte viability. The intent of this study was to determine the influence of the level of ischemic blood flow and the major determinants of myocardial O2 consumption (MVO2) (heart rate and systolic blood pressure) on recovery of CP during prolonged moderate myocardial hypoperfusion. 31P-nuclear magnetic resonance spectroscopy was used to measure CP, ATP, and Pi in the subepicardium (Epi) and subendocardium (Endo) of 13 open-chest dogs. Wall thickening was measured with sonomicrometry. A coronary stenosis reduced mean myocardial blood flow (microspheres) from 1.10 +/- 0.07 to 0.71 +/- 0.06 ml.g-1.min-1 (P < 0.01) and the Endo-to-Epi blood flow ratio from 1.12 +/- 0.07 to 0.59 +/- 0.06 (P < 0.01), and dyskinesis developed. Coronary blood flow and systolic wall thickening did not change significantly during 4 h of hypoperfusion. Epi CP and ATP fell to 80 +/- 4% (P < 0.05) and 93 +/- 3% of control, respectively, at 30 min. Epi CP then recovered to 87 +/- 5% while ATP decreased further to 83 +/- 5% of baseline by the end of the 240-min ischemic period. Endo CP and ATP fell to 53 +/- 4 and 77 +/- 5% of control, respectively, at 30 min; then Endo CP recovered to 85 +/- 6% while ATP decreased further to 68 +/- 6% of baseline at 240 min of hypoperfusion. ADP levels were significantly increased at 30 min but recovered to baseline by 240 min of hypoperfusion. delta Pi/CP increased significantly (Endo > Epi) at the onset of ischemia and then progressively decreased. At 30 min, mild myocardial acidosis was observed in some hearts with variable pH recovery during continuing hypoperfusion. The data demonstrate that variations in blood flow cannot account for the magnitude of the initial fall in CP or for the final extent of recovery. However, the rate at which CP recovered was significantly correlated with the level of blood flow. Variations in the determinants of MVO2 did not account for differences in CP recovery.

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Cytosol; Dogs; Endocardium; Energy Metabolism; Heart; Heart Rate; Hemodynamics; Hibernation; Magnesium; Myocardial Ischemia; Myocardium; Oxygen Consumption; Phosphocreatine; Regional Blood Flow; Regression Analysis; Systole; Time Factors

31P metabolite measurements in the human heart by magnetic resonance spectroscopy (MRS) have been reported previously. By use of a method in which metabolite content was quantified with reference to a standard located outside the chest, it has become possible to measure the content of phosphocreatine (PCr) and ATP in vivo in the human heart. In this study, PCr and ATP contents were measured by 31P MRS and compared in human myocardium with reversible ischemia or scar diagnosed by exercise thallium scintigraphy.. Forty-one subjects with stenosis of the left anterior descending coronary artery (> 50%) and 11 healthy control subjects (C) composed the present study group. Patients were divided into two groups on the basis of exercise 201Tl scintigraphy: a reversible 201Tl defect group (RD[+], n = 29) who demonstrated redistribution at late image and a fixed 201Tl defect group (RD[-], n = 12). While the subjects lay supine within the magnet, 31P MR spectra were obtained from the anterior and apical regions of the left ventricle by slice-selected one-dimensional chemical shift imaging. For metabolite quantification, a standard was placed at the center of the surface coil. ANOVA revealed significant differences among the three groups with respect to the mean (+/- SD) PCr at rest (C, 12.14 +/- 4.25 > RD[+], 7.64 +/- 3.00 > RD[-], 3.94 +/- 2.21 mumol/g wet heart tissue, P < .05) as well as a significant decrease in ATP in the RD(-) group (C, 7.72 +/- 2.97; RD[+], 6.35 +/- 3.17 > RD[-], 4.35 +/- 1.52 mumol/g wet heart tissue, P < .05).. Compared with healthy control subjects, PCr content decreased significantly in patients with both reversible and fixed 201Tl defects, and ATP content decreased significantly in subjects with fixed thallium defects. These results suggest that the measurement of ATP content in the human heart by 31P MRS is a clinically important method for the evaluation of myocardial viability.

Topics: Adenosine Triphosphate; Adult; Aged; Coronary Disease; Female; Humans; Magnetic Resonance Spectroscopy; Male; Middle Aged; Myocardium; Phosphocreatine; Thallium Radioisotopes; Tomography, Emission-Computed, Single-Photon

Metabolic behavior was compared during acute extracorporeal reperfusion after removal of a chronic 4-day partial coronary stenosis in eight pig hearts (RCS group) and during comparable extracorporeal perfusion in seven chronically prepared hearts (Sham group). Coronary stenosis in RCS hearts was induced in the left anterior descending (LAD) artery by partial inflation of a hydraulic occluder to restrict LAD peak phasic velocity by approximately 50%. Regional mechanical shortening was decreased in RCS compared with Sham hearts after 4 days of chronic coronary stenosis [diminished systolic shortening (P < 0.066) with systolic expansion (P < 0.015)] but was comparable to Sham hearts after relief from stenosis. At analogous workloads (left ventricular pressure and heart rate) during reperfusion, metabolic behavior was distinctive between groups. Specifically, compared with Sham hearts, myocardial O2 consumption was selectively increased in RCS hearts (+ 49 delta %, P < 0.026) as was fatty acid oxidation estimated from 14CO2 production from [U-14C]palmitate (+ 60 delta %, P < 0.061) and exogenous glucose utilization measured from the release of 3H2O from [5-3H]glucose (+ 517 delta %, P < 0.025). At the conclusion of the studies, triphenyltetrazolium chloride staining showed no gross evidence of macroinfarction in RCS or Sham hearts, and there was an essentially unremarkable histological survey of anterior myocardium for microscopic necrosis in either group. The level of O2 consumption and preservation of preferred fatty acid utilization indicate that metabolism remains or regains its aerobic pattern of activity in early recovery immediately after removal of chronic partial coronary stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Carbon Dioxide; Coronary Disease; Energy Metabolism; Glucose; Heart; Myocardial Reperfusion; Myocardium; Oxygen Consumption; Palmitic Acid; Palmitic Acids; Phosphocreatine; Reference Values; Swine; Systole

Changes in ATP and creatine phosphate levels during early (up to 150 s) global ischaemia were determined in isolated rat hearts by two chemical extraction methods (a conventional direct perchloric acid extraction and a stepwise extraction using alcohol and perchloric acid solutions) and by qualitative 31P-NMR. No difference in the ATP level hardly changed up to 40 s of ischaemia when measured by the three methods, and slightly decreased at 150 s of ischaemia. In contrast to ATP, creatine phosphate content in the normally perfused tissue was observed to be higher by the stepwise extraction (68-73 nmol/mg protein) than by direct perchloric acid extraction (55 nmol/mg protein). The creatine phosphate rapidly decreased to about 50% of normal value at 40 s of ischaemia, and the difference in the normal creatine phosphate content using the two chemical methods disappeared with the progression of ischaemia. Thus, the creatine phosphate more rapidly decreased when observed by the stepwise method than by the other two methods in this ischaemic condition. These results suggest that (1) creatine phosphate exists in an undetermined chemical state (perhaps neither in simple soluble form nor in so-called "bound" form) in rat cardiac myocytes, and (2) the stepwise extraction method is useful to measure the content of energy metabolites and to examine the intracellular chemical state in cardiac tissues.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Ethanol; Evaluation Studies as Topic; In Vitro Techniques; Magnetic Resonance Spectroscopy; Male; Methods; Myocardium; Perchlorates; Perfusion; Phosphocreatine; Phosphorus; Rats; Rats, Wistar

The metabolic changes of myocardial ischemia in patients with coronary artery disease assessed by 31P magnetic resonance spectroscopy (MRS) have been reported previously. A significant decrease in the ratio of phosphocreatine (PCr) to ATP during handgrip exercise in a group of patients with severe coronary artery disease has been demonstrated. However, there are no reports at present that directly compare cardiac 31P MRS data with exercise 201Tl myocardial scintigraphy, now established as one of the most important clinical methods to assess myocardial ischemia. The purpose of this study was to investigate whether 31P MRS with handgrip exercise testing is able to detect myocardial ischemia, demonstrated by exercise 201Tl scintigraphy.. Twenty-seven patients with severe stenosis of the left anterior descending coronary artery (> or = 75%) and 11 normal control subjects composed the present study. Patients were divided into two groups on the basis of exercise 201Tl scintigraphy: a reversible 201Tl defect group (RD[+]) who demonstrated redistribution at the late image and a fixed 201Tl defect group (RD[-]). While lying supine within the magnet, subjects performed handgrip exercise at 30% of maximal force once in every two cardiac cycles. 31P MR spectra were collected before and during handgrip exercise. Data were corrected for the saturation factor. ANOVA revealed significant differences among the three groups with respect to the mean +/- SD PCr/ATP ratio at rest (control, 1.85 +/- 0.28 > RD(+), 1.60 +/- 0.19 > RD(-), 1.24 +/- 0.30; P < .05). The PCr/ATP ratio decreased significantly from 1.60 +/- 0.19 at rest to 0.96 +/- 0.28 during exercise (P < .001) in the RD(+) group (n = 15). However, in the RD(-) group (n = 12), the ratio did not change significantly during handgrip exercise (1.24 +/- 0.30 at rest versus 1.19 +/- 0.28 during exercise). Similarly, the ratio did not change in the control group (n = 11) (1.85 +/- 0.28 at rest versus 1.90 +/- 0.23 during exercise).. Contrary to normal subjects or patients with fixed thallium defects, the PCr/ATP ratio was significantly altered by exercise in patients with reversible thallium defects. These results suggest that 31P MRS with handgrip exercise testing is a sensitive method for detecting myocardial ischemia.

Topics: Adenosine Triphosphate; Coronary Disease; Exercise; Exercise Test; Female; Heart; Humans; Magnetic Resonance Spectroscopy; Male; Middle Aged; Myocardial Ischemia; Myocardium; Phosphocreatine; Sensitivity and Specificity; Thallium Radioisotopes; Tomography, Emission-Computed, Single-Photon

Topics: Adult; Coronary Disease; Forearm; Humans; Hydrogen-Ion Concentration; Middle Aged; Muscles; Muscular Diseases; Phosphocreatine; Syndrome

The response of the myocardium to prolonged or chronic ischemia may differ from the well documented changes that occur acutely subsequent to the onset of hypoperfusion. Therefore, we have examined in an instrumented canine model and using spatially localized spectroscopy to achieve transmural differentiation, the myocardial HEP and Pi levels as well as wall thickening in situ during prolonged ischemia induced by sustained coronary artery stenosis. The results demonstrate that subtotal coronary artery occlusion causes immediate and transmurally inhomogeneous decreases in the myocardial HEP content and increase in the Pi/CP ratio; however, during prolonged mild hypoperfusion, metabolic changes occur which lead to statistically significant recovery of CP (but not ATP) and disappearance of Pi despite the persistence of reduced blood flow and oxygen supply. Upon release of the occlusion, the previously ischemic muscle recovered blood flow, and some (but not all) of its preischemic contractile function without parallel changes in the HEP levels. It is concluded that normal HEP and Pi levels cannot be equated with either the absence of underperfusion or insensitivity of NMR spectroscopy to ischemia. Rather, it is imperative that both functional and spectroscopic measurements are performed simultaneously to distinguish between ischemic myocardium which is adapted versus unadapted to the hypoperfusion.

Topics: 2,3-Diphosphoglycerate; Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Diphosphoglyceric Acids; Dogs; Endocardium; Heart Ventricles; Magnetic Resonance Spectroscopy; Myocardial Ischemia; Myocardium; Pericardium; Phosphates; Phosphocreatine; Phosphorus; Time Factors

The authors submit their experience with the use of creatine phosphate in patients operated on account of coronary heart disease. They divided 50 consecutive patients into three groups. Group A--controls, group B--creatine phosphate was added to the filling of the apparatus for extracorporeal circulation and group C--creatine phosphate was added to Bretschneider's cardioplegic solution. During operation and during the early postoperative period the CK and CK MB levels were evaluated as well as levels of free acid radicals, the haemodynamic state of the patients, the incidence of ventricular dysrhythmias, the need of defibrillation, histological and histochemical examinations. The authors found a lower CK and CK MB level, a lower percentage of ventricular dysrhythmias and the same haemodynamic results of the operation in patients with a more markedly impaired systolic function of the left ventricle when creatine phosphate was used. Creatine phosphate did not affect the morphology of the heart muscle nor the level of the assessed myocardial enzymes.

Topics: Cardioplegic Solutions; Coronary Disease; Creatine Kinase; Extracorporeal Circulation; Female; Free Radicals; Hemodynamics; Humans; Isoenzymes; Male; Middle Aged; Phosphocreatine; Postoperative Complications; Prospective Studies

The role of Ca2+ in the manifestation of the cardioprotective effect of phosphocreatine (PCr) on the ischemic myocardium was studied in isolated rat hearts perfused by the Langendorf method. Under ischemic cardiac arrest induced by a Ca(2+)-free perfusing solution PCr had no protective effect on the ischemic myocardium. PCr accelerated the postischemic restoration of contractility of hearts perfused with a solution containing 0.5 and 1.2 mM Ca2+. The structural analog of PCr, phosphoarginine, possessing a Ca(2+)-binding capacity similar to that of PCr, had no protective effect. The effects of PCr and Ca2+ on the package of sarcolemmal vesiculate lipids were studied by ESR spectroscopy. PCr induced a more dense package of membrane phospholipids at weakly acidic and neutral values of pH (but not at pH 8.5). Although at pH 5.5 Ca2+ did not affect the membrane structure, it potentiated the effect of PCr on sarcolemmal phospholipids. Thus, the protective effect of PCr on the ischemic myocardium is not linked with its ability to bind Ca2+; however, Ca2+ is an indispensable component of the mechanism underlying the protective effect of PCr on the ischemic myocardium.

Topics: Animals; Arginine; Calcium; Cations, Divalent; Coronary Disease; Electron Spin Resonance Spectroscopy; Heart; In Vitro Techniques; Male; Myocardium; Organophosphorus Compounds; Phosphocreatine; Rats; Rats, Inbred Strains; Spin Labels

This study was designed to compare the effects of the calcium slow channel blocking agents verapamil (0.15 mg/kg), diltiazem (0.15 mg/kg), and nifedipine (50 micrograms/kg) on the myocardium after global ischemia and reperfusion in the in situ canine model. Animals were subjected to 120-min normothermic global ischemia, followed by 45-min reperfusion. Cardioplegic arrest of the myocardium was achieved by administering one of the three calcium antagonists in a multidose fashion. Superior preservation (p less than 0.01) of left ventricular (LV) systolic function was achieved in group I (verapamil cardioplegia). dP/dt, at an intraventricular balloon volume of 25 cc, was 83% of control after reperfusion in group I. Group II (diltiazem) and group III (nifedipine) achieved only 55 and 63% of their preischemic dP/dt values. LV chamber stiffness was increased in hearts protected with nifedipine. The exponential constant m was increased from 0.04 +/- 0.01 to 0.08 +/- 0.01. Coronary blood flow after reperfusion increased from 120 to 184 cc/100 gr/min in group I (p less than 0.01). The hyperemic response in group III was negligible. The O2 consumption of the reperfused myocardium was not significantly altered in any of the treatment groups. Lactate metabolism during ischemia and after reperfusion was similar in all groups. ATP values were markedly reduced in all groups (p less than 0.05). Immediately after ischemia, ATP was 50, 28, and 44% of control in group I, II, and III, respectively. The excellent preservation of systolic function and a physiologic hyperemic response by verapamil could not be correlated with improved preservation of high-energy compounds or with significant changes in myocardial O2 consumption.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Animals; Calcium Channel Blockers; Coronary Circulation; Coronary Disease; Dogs; Heart Arrest, Induced; Myocardial Reperfusion; Myocardium; Oxygen Consumption; Phosphocreatine; Vasodilation

Calcium antagonists are useful for the management of patients with ischaemic heart disease, particularly when used prophylactically. At the cellular level, these drugs act primarily by limiting calcium ion (Ca++) entry through the voltage-sensitive Ca(++)-selective channels, an effect that contributes markedly to their 'energy sparing' properties. However, the long term use of these drugs has additional advantages, particularly with respect to their ability to slow Ca(++)-dependent processes involved in the formation of atherogenic lesions, partially antagonise the effects of the raised levels of circulating endothelin-1 encountered during ischaemia-induced heart failure and hypertension, and trap and immobilise oxyradicals. Prolonged episodes of ischaemia result in an irreversible loss of homeostasis with respect to Ca++. However, the increase in myocardial cytosolic Ca++ caused by relatively short periods of ischaemia is small, reversible, and markedly attenuated by the prophylactic use of calcium antagonists. In the isolated, perfused rat heart, verapamil pretreatment produces statistically significant inhibition of the increase in cytosolic Ca++ during 20-minute global ischaemia. This stereospecific effect is associated with a decrease in the rise in total tissue Ca++ during reperfusion and amelioration of the adenosine triphosphate depletion caused by ischaemia. In general, discussion relating to the molecular basis of the use of calcium antagonists in the management of patients with ischaemic heart disease needs to take into account the duration of the ischaemic event, the workload on the myocardium, the need for prophylactic therapy, and the presence of exacerbating factors such as atherosclerosis and tobacco smoking. The early rise in cytosolic Ca++, the source of which remains uncertain, appears to be an important focus for anti-ischaemic drug therapy.

Topics: Adenosine Triphosphate; Animals; Calcium; Coronary Disease; Magnetic Resonance Spectroscopy; Male; Myocardial Reperfusion; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains; Verapamil

Previous studies on the possible antiarrhythmic effects of angiotensin converting enzyme (ACE) inhibitors during early ischemia in pigs have been inconclusive or negative; however, proof of adequate ACE inhibition was not provided. Perindoprilat, 0.06 mg/kg, i.v., was administered 30 min prior to ligation of the anterior descending coronary artery (CAL) in anesthetised open-chest pigs. Plasma ACE activity was decreased by 95.0 +/- 1.9% when measured 5 min before CAL. Within 5 min of CAL, the ventricular fibrillation threshold (VFT) in the control group was decreased from 11.8 +/- 1.9 to 7.2 +/- 1.2 mA (p less than 0.01). Perindoprilat prevented the fall in the VFT and the increase in left ventricular end-diastolic pressure caused by CAL. Perindoprilat decreased arterial pressure. Cardiac output (thermodilution) was decreased by 23 +/- 3% after CAL in the control group and by only 10 +/- 5% (p less than 0.05) in the perindoprilat group (both versus pre-CAL values). In the control group cyclic AMP was increased from 0.97 +/- 0.04 (pre-CAL) to 1.16 +/- 0.04 nmol/g (p less than 0.05) in the central ischemic zone 20 min after CAL. Perindoprilat prevented this increase in cyclic AMP. Twenty minutes after CAL blood flow (microsphere method) in the nonischemic zone of the perindoprilat group was increased, whereas blood flow in the central ischemic zone was decreased compared to the control group. However, levels of tissue metabolites (ATP, phosphocreatine, lactate) measured in drill biopsies in the same zones of the two groups were similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Angiotensin-Converting Enzyme Inhibitors; Animals; Anti-Arrhythmia Agents; Blood Pressure; Coronary Circulation; Coronary Disease; Female; Heart Rate; Indoles; Lactates; Male; Myocardium; Peptidyl-Dipeptidase A; Phosphocreatine; Swine; Ventricular Fibrillation

The effects of transient low Ca2+ reperfusion after ischaemia on metabolic and functional recovery were studied in isolated rat hearts.. 31P nuclear magnetic resonance (NMR) was used to monitor creatine phosphate, ATP, intracellular inorganic phosphate (Pi), and intracellular pH during control perfusion (15 min), total ischaemia (30 min), and reperfusion (30 min). During early reperfusion (0-10 min) perfusate [Ca2+] amounted to 1.3 (control group), 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, or 0.7 mmol.litre-1. During late reperfusion (10-30 min) perfusate [Ca2+] was 1.3 mmol.litre-1. Isolated rat hearts were used and perfused according to Langendorff.. Recovery of creatine phosphate during early reperfusion was partly abolished during late reperfusion in the 0.1-0.4 mmol.litre-1 groups (p < 0.01). In the 0.1 mmol.litre-1 group creatine phosphate content after 30 min reperfusion was lower (p < 0.05) than in the control group. Recovery of ATP during early reperfusion in the 0.3 mmol.litre-1 group was better than in the control group (p < 0.01). After 30 min reperfusion ATP recovery was better in the 0.3 mmol.litre-1 group (p < 0.01) and worse in the 0.1 mmol.litre-1 group (p = 0.05) than in the control group. Decline of Pi during early reperfusion was more pronounced in the 0.2 and 0.3 mmol.litre-1 groups (p < 0.01) and in the 0.5 and 0.6 mmol.litre-1 groups (p < 0.05) than in the control group. In the 0.3 and 0.4 mmol.litre-1 groups, Pi after 30 min reperfusion was higher (p < 0.05) than after 10 min reperfusion. After 30 min reperfusion left ventricular developed pressure, measured with an intraventricular balloon, was lower in the 0.1 mmol.litre-1 group (p < 0.01) than in the control group.. The data show that under the experimental conditions used successive postischaemic reperfusion with 0.1 and 1.3 mmol.litre-1 Ca2+ resulted in poorer metabolic and functional recovery of the hearts than continuous reperfusion with 1.3 mmol.litre-1 Ca2+. Postischaemic reperfusion with 0.1 mmol.litre-1 Ca2+ may predispose the heart to a mild calcium paradox. Successive reperfusion with 0.3 and 1.3 mmol.litre-1 Ca2+ was optimal in terms of ATP recovery but did not result in an increased recovery of left ventricular developed pressure.

Topics: Adenosine Triphosphate; Animals; Calcium; Coronary Disease; Drug Administration Schedule; Heart; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Male; Myocardial Reperfusion; Myocardium; Perfusion; Phosphates; Phosphocreatine; Rats; Rats, Wistar

The age-related response of the myocardium to 30 min of 37 degrees C global ischemia and 120 min of 37 degrees C reperfusion, measured by phosphorus-31 magnetic resonance spectroscopy and the recovery of isovolumic function, was evaluated by using perfused neonatal (3-8 days old, n = 10), immature (24-30 days old, n = 10), and adult (2-4 mo old, n = 5) rabbit hearts. Basal intracellular pH (pHi) was highest in neonatal hearts and decreased with age. The basal phosphocreatine (PCr)-to-ATP ratio differed in each group, increasing with age. Rapid depletion of PCr occurred in all groups during ischemia; ATP retention was greater in adults than in neonates. Reperfusion resulted in no measurable recovery of ATP in any group. Postischemic pHi stabilized above preischemic values in neonatal and immature hearts and below preischemic values in adult hearts. Recovery of PCr and cytosolic Pi (Pcyi) content, heart rate, and coronary flow during reperfusion was greater in neonatal and immature than in adult hearts. During the final 20 min of ischemia, pHi was lower in immature than in neonatal or adult hearts. Postischemic recovery of left ventricular maximum rate of pressure rise (+dP/dtmax) was depressed in immature compared with neonatal and adult hearts. These results demonstrate increased tolerance of the neonatal heart and increased susceptibility of the immature heart to unprotected normothermic ischemic injury relative to the adult heart and suggest that maturational changes in myocardial pHi regulation may be responsible for the observed age-related response.

Topics: Adenosine Triphosphate; Aerobiosis; Aging; Animals; Body Temperature; Coronary Disease; Energy Metabolism; Hydrogen-Ion Concentration; In Vitro Techniques; Intracellular Membranes; Magnetic Resonance Spectroscopy; Myocardial Reperfusion; Myocardium; Phosphocreatine; Phosphorus; Rabbits

1. The postulate that the composition of solutions used to reperfuse ischaemic hearts may modulate their ability to synthesize high-energy compounds was tested in isolated rat hearts subjected to 30 min normothermic ischaemia and then reperfused with either Krebs'-Henseleit buffer (K-H) for 20 min (control reperfusion, CR), or a 'myocardial protective solution' (MPS) for 5 min, followed by 15 min K-H (modified reperfusion, MR). The 'myocardial protective solution' was designed to protect against damage caused by sodium and calcium accumulation and by free radicals. Metabolic precursors were also included to promote and support adenosine triphosphate (ATP) resynthesis during reperfusion under both aerobic and hypoxic conditions. 2. 31P nuclear magnetic resonance (NMR) was used to measure tissue ATP and creatine phosphate (CP), and atomic absorption spectrometry was used to measure Ca++. Early during CR, ATP recovered to 28% of the pre-ischaemic value, but fell to 5.5% with continued perfusion. Similarly, CP recovered to 45.5% of the pre-ischaemic level during early CR but fell to 25.5% with continued perfusion. 3. Better maintenance of ATP was seen during MR with oxygenated MPS (O2-MR), the final ATP remaining at 16.9% of the pre-ischaemic level. During O2-MR, CP recovered to 43.55 of the pre-ischaemic level but was not maintained and fell to a final level of 29.5%. 4. During MR with O2-free MPS (non-O2-MR), there was no reperfusion-associated fall in ATP or CP, with the levels maintained at 26.6% and 34.55, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Animals; Calcium; Coronary Disease; Female; Male; Myocardial Reperfusion; Myocardial Reperfusion Injury; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains

To assess the effect of carteolol, a beta-blocker, on ischemia and reperfusion, changes in the ultrastructure of myocytes and energy metabolism were studied by 31P-NMR in 41 pig hearts without collateral circulation. The left anterior descending coronary artery was occluded for 20 min and reperfused for 120 min in three groups: seven pigs (group 1, no treatment with carteolol; group 2, pre-ischemia treatment with carteolol (10 micrograms/kg); group 3, post-ischemia treatment with carteolol before reperfusion). Other groups of five pigs were killed after 120 min of ischemia (group 4, no treatment; group 5, pre-ischemia treatment) or 20 min of ischemia (group 6, no treatment; group 7, pre-ischemia treatment). After 20 min of ischemia, ATP was higher in groups 2 (76 +/- 9% of the baseline value) than in group 1 (59 +/- 5%) and group 3 (60 +/- 10%). However, the difference disappeared after 30 min of ischemia. After 120 min of reperfusion, ATP showed much better recovery in group 2 (92 +/- 9%) than in groups 1 (66 +/- 7%) and 3 (68 +/- 10%). Ischemic injury, as viewed by light and electron microscopy, was milder in group 7 than in group 6 after 20 min occlusion, but the myocytes were almost normal after 120 min reperfusion in groups 1 to 3. The heart rate, blood pressure and rate pressure product showed no significant difference among the groups. These results indicate that pre-ischemia treatment with carteolol provided protection against ischemic cellular injury and accelerated the repletion of ATP during reperfusion, but the post-ischemia treatment did not lead to recovery of ATP. Therefore, the favorable effect during reperfusion of pre-ischemia treatment with carteolol depends on its protective effect during ischemia.

Topics: Adenosine Triphosphate; Animals; Carteolol; Coronary Disease; Hemodynamics; Hydrogen-Ion Concentration; Kinetics; Magnetic Resonance Spectroscopy; Microscopy, Electron; Myocardial Reperfusion; Myocardium; Phosphates; Phosphocreatine; Swine

Difficulties in studying myocardial metabolism with adequate time resolution have led to contradictory conclusions regarding the mechanisms causing contractile abnormalities during the early stages of ischemia. In acutely instrumented swine, we investigated whether abnormalities in subendocardial ATP, phosphocreatine, or lactate content develop rapidly enough during the first few heart beats after onset of partial myocardial ischemia to contribute to contractile failure. Within the first 15 beats of a 40-50% reduction in left anterior descending coronary artery blood flow, regional myocardial function was significantly reduced but continuing to deteriorate. Rapidly frozen transmural left ventricular biopsies obtained on the 15th heart beat (+/- 1.5 beats) after the onset of ischemia revealed significant decrements in subendocardial phosphocreatine and ATP levels to 77% (p less than 0.05) and 84% (p less than 0.005) of control values, respectively, but minimal change in lactate content. Metabolic effects as assessed by transmural averages took longer to become detectable; thus, there was a tendency to underestimate the importance of subendocardial metabolic effects on myocardial function. When left ventricular preload was assessed during this early time period, left ventricular end-diastolic wall thickness only decreased by 3%, and left ventricular end-diastolic pressure did not change significantly despite a large fall in coronary perfusion pressure. Thus, in an in vivo pig model with techniques optimized to detect subendocardial metabolic changes within the period of very early moderate myocardial ischemia, abnormalities in high energy phosphate compounds occurred rapidly enough to contribute to developing myocardial dysfunction, whereas preload-mediated mechanisms related to vascular distending pressure could not explain the functional deterioration under these conditions.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Electrocardiography; Energy Metabolism; Female; Hemodynamics; Lactates; Male; Myocardial Contraction; Myocardium; Phosphocreatine; Swine; Time Factors

The hypothesis that aspartate and 2-oxoglutarate might help to relieve the inhibition of glycolysis during global myocardial ischaemia and improve post-ischaemic mechanical recovery was tested in isolated rat hearts. The hearts were attached to a lumped parameter model of the rat vascular impedance and initially perfused in the working mode with buffered Krebs-Henseleit solution containing 10.1 mmol/l glucose, with or without 3.3 mmol/l of aspartate and 3.3 mmol/l of 2-oxoglutarate, prior to imposing global ischaemia for 5, 10 or 15 mins. The addition of aspartate and 2-oxoglutarate improved the preservation of tissue CP after 5 mins of ischaemia and of ATP after 10 mins of ischaemia. The total adenine nucleotide pool was higher in the supplemented hearts after all three periods of ischaemia. Dihydroxyacetone phosphate, alanine, succinate and lactate accumulated during ischaemia, but the dihydroxyacetone phosphate accumulation was reduced while the alanine and succinate concentrations were increased by the addition of aspartate and 2-oxoglutarate to the perfusate. These observations lend support to the hypothesis that ischaemia arrests glycolysis at the glyceraldehyde phosphate dehydrogenase step due to a lack of oxidised nicotinamide adenine dinucleotide. Increasing the substrate concentrations of aspartate and 2-oxoglutarate may permit glycolysis to proceed for longer into the period of ischaemia by stimulating an additional pathway for nicotinamide adenine dinucleotide reoxidation. Small improvements in mechanical recovery were associated with the metabolic changes.

Topics: Adenine Nucleotides; Animals; Aspartic Acid; Coronary Disease; Glycolysis; In Vitro Techniques; Ketoglutaric Acids; Male; Myocardial Contraction; Perfusion; Phosphocreatine; Rats; Rats, Inbred Strains

We administered fructose-1,6-bisphosphate (FDP), 1 mM, to isolated and perfused rabbit hearts submitted, after 90 minutes of equilibration, to an ischemic period (60 minutes at a coronary flow of 0.17 ml/min/g), followed by a period of reperfusion (30 minutes at a coronary flow of 3.6 ml/min/g). FDP was delivered at different times following the experimental protocol: 60 minutes before ischemia and for the entire experiment; 60 minutes before and during ischemia, but not at reperfusion; at the onset of ischemia and during reperfusion; and only during reperfusion. The FDP cardioprotective effect was evaluated in terms of recovery of left ventricular pressure developed during reperfusion, creatine phosphokinase (CPK) and noradrenaline release, mitochondrial function (expressed as yield, RCI, QO2, ADP/O), ATP and creatine phosphate (CP) tissue contents, calcium homeostasis, and by measuring oxidative stress in terms of reduced and oxidized glutathione release and tissue contents. Our data show that the cytoprotective action of FDP is closely related to the time of administration. Optimal myocardial preservation was achieved when it was present prior to ischemia and during reperfusion. When given at the time of ischemia or only on reperfusion, FDP does not exert cardioprotection. The data suggest that the FDP cardioprotective effect is related to improvement of energy metabolism.

Topics: Adenosine Triphosphate; Animals; Calcium; Coronary Disease; Creatine Kinase; Drug Administration Schedule; Fructosediphosphates; Glutathione; Heart; In Vitro Techniques; Male; Mitochondria, Heart; Myocardial Reperfusion Injury; Norepinephrine; Oxidation-Reduction; Oxygen Consumption; Phosphocreatine; Rabbits; Ventricular Function, Left

We studied the effects of angiotensin II during low-flow ischemia and reperfusion using red cell-perfused isovolumic rabbit hearts. Under baseline conditions where coronary perfusion pressure (CPP) was 100 mm Hg and left ventricular end-diastolic pressure (LVEDP) was set at 10 mm Hg, 10(-8) M angiotensin II caused a mild increase in LV developed pressure (+12%) and decrease in coronary flow (-8%). Low-flow ischemia was imposed by reducing CPP to 15 mm Hg for 30 min followed by 30 min of reperfusion. During ischemia, the angiotensin II group showed a gradual further reduction in coronary flow in association with a greater depression of LV developed pressure and increase in LVEDP relative to the no-drug group. To separate the effect of angiotensin II on coronary flow from a direct myocardial effect, the angiotensin II group was compared with an additional no-drug group with a matched progressive reduction in coronary flow during ischemia. In these groups, the ischemic depression of LV developed pressure, myocardial ATP levels, and lactate production were similar. However, the ischemic rise in LVEDP was greater (42.0 +/- 5.4 vs. 19.9 +/- 1.3 mm Hg, P less than 0.01) and recovery was incomplete in the angiotensin II group. These observations suggest that angiotensin II exerts a direct adverse effect on LV diastolic relaxation during low-flow ischemia and recovery.

Topics: Adenosine Triphosphate; Angiotensin II; Animals; Calcium; Coronary Circulation; Coronary Disease; Energy Metabolism; Erythrocytes; In Vitro Techniques; Male; Myocardial Contraction; Myocardial Reperfusion; Phosphates; Phosphocreatine; Rabbits

The aim of this study was to determine whether acute changes in [Mg2+]free occur during increased hydrolysis of cytosolic ATP, and whether these changes were of sufficient magnitude to be involved in the modulation of myocardial metabolism. 31P-NMR was used to estimate free cytosolic Mg2+ levels ([Mg2+]free) during hypoxia, isoproterenol stimulation, and graded low-flow ischemia in crystalloid perfused, isovolumic rat hearts. Cytosolic [Mg2+]free was calculated to be 0.73 +/- 0.12 mM in control hearts (100 mmHg hydrostatic pressure, 95% O2, n = 18). Cytosolic [Mg2+]free increased gradually during 10 min periods of hypoxia (65%, 50%, 35%, 5% O2), and 20 min infusions of isoproterenol (0.4, 3.0, 75 nM), to maximum values greater than 250% of control (P less than 0.05). During 8 min periods of graded low-flow ischemia (12.0, 7.2, 5.3, 3.4, and 1.6 ml/min/g), [Mg2+]free did not change significantly. [Mg2+]free displayed an inverse linear correlation with total cytosolic [ATP] during isoproterenol infusion (r = 0.87), and an exponential correlation during hypoxia (r = 0.82). The data indicate that acute changes in cytosolic [Mg2+]free can occur during conditions of net ATP hydrolysis although changes in ATP alone do not appear to be solely responsible for the changes in [Mg2+]free. Since the magnitude of the changes in [Mg2+]free are sufficient to alter equilibria of enzymes such as creatine kinase and myokinase, it is possible that these changes are involved in the acute modulation of myocardial metabolism.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Cytosol; Hydrogen-Ion Concentration; Hypoxia; In Vitro Techniques; Isoproterenol; Magnesium; Magnetic Resonance Spectroscopy; Male; Myocardium; Perfusion; Phosphates; Phosphocreatine; Phosphorus Isotopes; Protons; Rats; Rats, Inbred Strains

The use of calcium antagonists as cardioprotective agents is based on the assumption that uncontrolled Ca2+ gain is a key factor in causing cell death and tissue necrosis. This uncontrolled gain in Ca2+ is the ultimate expression of a series of metabolic events triggered by inadequate perfusion. One of the early events is a rise in cytosolic Ca2+ (Cai2+). Using 1,2-bis(e-amino-5-fluorophenoxy)ethan-N1N1N11N11tetraacetic acid and nuclear magnetic resonance spectroscopy to monitor this early rise in Cai2+, it is possible to show that, in isolated perfused rat hearts, Cai2+ increases (p less than 0.01) within the initial 10 min of ischemia and that the increase progresses with time. Possible causes of this early rise in Cai2+ include activation of the endothelin-1 receptors with the subsequent inositol triphosphate-induced activation of sarcoplasmic (SR) Ca2+ release, enhanced Ca(2+)-induced Ca2+ release from the SR reticulum, displacement of bound Ca2+ by the accumulating protons and entry of Ca2+ in exchange for Na+, or through the voltage-sensitive Ca2+ channels. Using the d and l isomers of verapamil it is possible to show that verapamil slows the early rise in Cai2+, the l isomer being more effective (p less than 0.01) than the d isomer. This, in addition to its established energy-sparing effect, may contribute to the effectiveness of verapamil as a cardioprotective agent when used prophylactically.

Topics: Adenosine Triphosphate; Animals; Calcium; Calcium Channel Blockers; Coronary Disease; Cytosol; Male; Myocardial Reperfusion; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains; Verapamil

The aim was to evaluate the protective effect of verapamil during myocardial ischaemia and reperfusion.. In vivo phosphorus-31 (31P) magnetic resonance spectroscopy was performed on rats pretreated with verapamil (mg.kg-1 intraperitoneal) and controls during a 45 min left coronary artery occlusion and 60 min reperfusion. In separate groups of animals, haemodynamic measurements were taken at baseline, during ischaemia, and during reperfusion. Infarct size was determined by staining with triphenyltetrazolium chloride.. Female Sprague-Dawley rats were used (control group n = 25, experimental group n = 24).. Infarct size was significantly reduced in the verapamil group compared to controls: 9.9(SEM 2.3)%, n = 19 v 28.5(2.7)%, n = 19, p less than 0.001 (infarct % of left ventricular mass). Myocardial phosphocreatine and ATP levels were reduced to similar levels in both verapamil and control animals after 45 min ischaemia: 56.8(3.4)%, n = 10, v 61.4(1.8)%, n = 11 NS; 67.7(2.7)%, n = 10 v 69.7(2.9)%, n = 11, NS (% of baseline value). After 60 min reflow, there was significant recovery of phosphocreatine [91.1(4.2)% of baseline, p less than 0.05] and ATP [86.8(2.7)% of baseline, p less than 0.05] in the verapamil group, but no recovery of high energy phosphates in controls [66.3(2.8), NS; 69.6(2.7), NS]. The left ventricular systolic pressure, heart rate, rate-pressure product, and maximum rate of left ventricular pressure development were similar prior to ischaemia, and during ischaemia in both groups. There was an inverse correlation between infarct size and the degree of phosphocreatine recovery after 60 min of reperfusion (PCr recovery (%) = -0.99 x infarct size (%) + 101; r = 0.91; p less than 0.01; n = 14). Furthermore, in a separate group of animals (n = 9), there was a significant correlation between the size of the ischaemic area at risk and the degree of phosphocreatine decline after 15 min of coronary occlusion (PCr reduction (%) = 0.91 x risk area (%) + 5.6; r = 0.97; p less than 0.01).. Pretreatment with verapamil extends the ischaemic time after which reperfusion results in myocardial salvage in this model of ischaemia and reperfusion. This protective effect is independent of the haemodynamic determinants of myocardial oxygen demand and the degree of ATP and phosphocreatine depletion during the ischaemic period. In this model of reversible ischaemia, 31P magnetic resonance spectroscopy is useful for quantitating both the size of the ischaemic region during coronary artery occlusion and infarct size after reperfusion.

Topics: Adenosine Triphosphate; Animals; Calcium; Coronary Circulation; Coronary Disease; Female; Hemodynamics; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Myocardial Reperfusion; Phosphocreatine; Rats; Rats, Inbred Strains; Verapamil

The aim was to attempt to get further insight into the mechanism of the cardioprotective action of phosphocreatine (PCr).. Three experimental protocols were used: (1) The effect was examined of exogenous PCr (10 mmol.litre-1) on myocardial oxidative damage produced by H2O2 perfusion (90 mumol.litre-1) of isolated rat heart. (2) Isolated rat hearts were subjected to 35 min cardioplegic ischaemia followed by reperfusion. A control group was studied along with two PCr groups, one corrected for Ca2+ to compensate its binding with PCr (1.4 mmol.litre-1 CaCl2 in St Thomas's Hospital cardioplegic solution), and the other not (1.2 mmol.litre-1). (3) The effect was studied of PCr alone and in combination with the antioxidant tocopherol phosphate (0.1 mumol.litre-1) on contractile and metabolic recovery of isolated rat heart reperfused after 40 min cardioplegic ischaemia.. Studies were performed on hearts of 84 male Wistar rats, weighing 250-300 g.. (1) Oxidative stress resulted in irreversible contracture and impairment of sarcolemmal integrity revealed by using the transmembrane tracer ionic lanthanum. These effects coincided with the decrease of developed pressure from 116 (SEM 3) to 38(3) mm Hg and rate-pressure product from 498(13) to 165(16) mm Hg.s-1. The Ca2+ binding property of PCr was estimated experimentally and the stability constant of the complex CaPCr was found to be 35.4(0.7) mmol; from this the Ca2+ bound by PCr was calculated to be 14% in the experimental conditions used. Ca2+ concentration in K-H buffer containing PCr was increased to compensate its binding with PCr. PCr prevented H2O2 induced contracture, preserved sarcolemmal integrity, and attenuated H2O2 induced decrease in developed pressure and rate-pressure product [73(6) mm Hg and 340(28) mm H.s-1, respectively, p less than 0.05 compared with control]. (2) PCr reduced the diastolic pressure [29(10) v 68(10) mm Hg in control group at 30 min of reperfusion, p less than 0.05] and enhanced the developed pressure [81(10) v 46(10) mm Hg in controls, p less than 0.05] and rate-pressure product [325(44) v 158(40) mm Hg.s-1 in controls, p less than 0.05]. When CaCl2 was increased to 1.4 mmol.litre-1 the protective effect of PCr was not abolished. (3) PCr resulted in improvement of developed pressure [49(7) v 18(5) mm Hg in controls at 40 min of reperfusion, p less than 0.05] and rate-pressure product [184(27) v 71(20) mm Hg.s-1 in controls, p less than 0.05]. The degree of contractile recovery in the tocopherol group was almost the same as in the PCr group. Combined addition of PCr and tocopherol further increased the developed pressure and rate-pressure product to 72(4) mm Hg and 284(23) mm Hg.s-1, respectively. Similarly, PCr and tocopherol in combination provided substantial inhibition of creatine kinase release into perfusate, at 3.8(0.4) v 10.9(2.5) IU in controls, p less than 0.05.. PCr decreases the vulnerability of myocardium to oxidative stress and ischaemic damage. These effects cannot be explained by PCr induced shifts in Ca2+ concentration. Protective effects of PCr and tocopherol are quantitatively additive, most probably due to their different mechanisms of action, and tocopherol may be effective in extending the ability of PCr to stabilise cell membrane structure.

Topics: Animals; Antioxidants; Calcium; Cardioplegic Solutions; Coronary Disease; Hydrogen Peroxide; In Vitro Techniques; Male; Myocardial Contraction; Myocardial Reperfusion Injury; Myocardium; Perfusion; Phosphocreatine; Rats; Rats, Inbred Strains; Vitamin E

We report in this study that the intracellular oxygenation state is measurable with the 1H nuclear magnetic resonance signal of the proximal histidine N delta H proton of deoxymyoglobin. The signal appears in a clear spectral region of the 1H spectrum and is sensitive to various hypoxic and ischemic conditions. In perfused heart, the deoxymyoglobin's response to tissue oxygenation precedes the one reflected in the 31P phosphocreatine or ATP signals, suggesting that oxidative energy metabolism is still sufficient even when the myoglobin is partially saturated with oxygen. Our method offers then a unique way to observe tissue oxygenation and its interaction in localized tissue region in vivo.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Hypoxia; Magnetic Resonance Spectroscopy; Male; Myocardium; Myoglobin; Oxygen Consumption; Phosphates; Phosphocreatine; Phosphorus; Rats; Rats, Inbred Strains

Hyperkalaemia-induced hypopolarization of the sarcolemnal membrane during standard crystalloid cardioplegic arrest potentiates calcium influx during reperfusion and is associated with depletion of high-energy phosphate reserves. Adenosine has been shown to induce fast cardiac arrest whilst preserving membrane hyperpolarization in an isolated rat heart model. In this study we compared the efficacy of adenosine, both as an arresting agent and as an ultrastructural, haemodynamic and high-energy phosphate preserving agent, in an in situ global ischemia model in the baboon with St. Thomas' Hospital solution No. 2 (ST2; n = 8) and with Krebs-Henseleit buffer (KHB; n = 7). The addition of 10 mM adenosine to the non-cardioplegic KHB (ADO; n = 8) improved haemodynamic recovery significantly in terms of cardiac index (91.6% +/- 7.2 vs 59.9% +/- 9.9) and stroke volume index (101.6% +/- 8.9 vs 55.6 +/- 10.0) and was not statistically distinguishable from the ST2 with regard to cardiac index (91.6% +/- 7.2 vs 94.8% +/- 5.8), stroke volume index (101.6% +/- 8.9 vs 114.0% +/- 8.3) or left ventricular dP/dt (73.1% +/- 9.9 vs 87.0% +/- 12.4). Adenosine triphosphate was best preserved with ADO (103.5% +/- 21.1 vs 67.9% +/- 9.3 and 48.5% +/- 8.7) although this was not statistically significant. This suggests therefore that the mechanism of cardioprotection by adenosine occurs by means other than its role as high-energy phosphate precursor.

Topics: Adenosine; Adenosine Triphosphate; Animals; Cardioplegic Solutions; Coronary Disease; Heart Arrest, Induced; Hemodynamics; Myocardial Reperfusion Injury; Papio; Phosphocreatine; Time Factors

The effects of L-propionylcarnitine on mechanical function, creatine phosphate and ATP content, and lactate dehydrogenase leakage were studied in isolated perfused rat hearts exposed to global no-flow ischemia for 30 min followed by reperfusion for 20 min. Five and 10 mM L-propionylcarnitine resulted in a 100% recovery of left ventricular-developed pressure, whereas the recovery was only 40% in the hearts perfused without this agent. Ischemia-reperfusion caused a 85% loss of creatine phosphate and a 77% loss of ATP, which was prevented by 10 mM L-propionylcarnitine. Five millimolar L-propionylcarnitine protected the heart from the loss of creatine phosphate but not from the loss of ATP. Ten millimolar L-propionylcarnitine failed to improve the postischemic left ventricular-developed pressure, when it was added to the perfusate only after ischemia. L-propionylcarnitine alleviated the decrease of coronary flow in the reperfused hearts. Lactate dehydrogenase leakage was aggravated in the beginning of the reperfusion period by 10 mM L-propionylcarnitine. This adverse effect was, however, transient. L-Propionylcarnitine provides protection for the postischemic reperfused heart in a dose-dependent manner. The optimal time for administration is before the ischemic insult. High doses of this compound may perturb cell membrane integrity. Moreover, the present data point to an intracellular, metabolic, and perhaps anaplerotic mechanism of action of L-propionylcarnitine in cardiac ischemia-reperfusion injury.

Topics: Animals; Blood Pressure; Carnitine; Coronary Circulation; Coronary Disease; Female; In Vitro Techniques; L-Lactate Dehydrogenase; Magnetic Resonance Imaging; Mitochondria, Heart; Myocardial Contraction; Myocardial Reperfusion Injury; Myocardium; Phosphocreatine; Phosphorus Isotopes; Rats; Rats, Inbred Strains; Ventricular Function, Left

High buffer cardioplegia may provide protection against ischemic damage by reducing the extent of intracellular acidosis. Secondary cardioplegia may improve postischemic recovery by restoration of high energy phosphates, ionic gradients, and intracellular pH. To test these hypotheses, pig hearts were arrested with high buffer (150 mM MOPS) cardioplegia or modified St. Thomas' solution II and then kept ischemic at 12 degrees C for 8 h. High energy phosphates and intracellular pH were followed during the period of ischemia, using 31P nuclear magnetic resonance spectroscopy, and functional recovery was followed during reperfusion. The hearts arrested by high buffer cardioplegia showed significantly higher intracellular pH than hearts preserved with St. Thomas' solution, but there were no significant differences in high energy phosphates. There were no significant differences in functional recovery. We found, however, that secondary cardioplegia abolished ventricular fibrillation, and resulted in improved functional recovery after 8 h of ischemic preservation compared with the hearts reperfused with Krebs-Henseleit solution alone. Our results suggest that despite attenuating the decreases in intracellular pH, high buffer cardioplegia does not improve recovery following 8 h of preservation at 12 degrees C. Secondary cardioplegia reduces the incidence of ventricular fibrillation and improves postischemic functional recovery of the myocardium.

Topics: Adenosine Triphosphate; Animals; Bicarbonates; Buffers; Calcium; Calcium Chloride; Cardioplegic Solutions; Coronary Disease; Cryopreservation; Dose-Response Relationship, Drug; Female; Heart; Hydrogen-Ion Concentration; In Vitro Techniques; Intracellular Fluid; Magnesium; Magnetic Resonance Spectroscopy; Male; Myocardial Reperfusion Injury; Myocardium; Organ Preservation; Phosphocreatine; Phosphorus; Potassium Chloride; Sodium Chloride; Swine

To determine the possible application of exogenous phosphocreatine (ePC) to protect the ischemic myocardium from reperfusion abnormalities in cardiac rhythm, the antiarrhythmic and antifibrillatory activities of the agent were studied in an acute myocardial ischemia model and reperfusion-induced cardiac damage. It was shown that ePC produced a pronounced antifibrillatory effect in acute coronary occlusion and subsequent reperfusion. The agent substantially increased the threshold of electric ventricular fibrillation and the frequency of spontaneous defibrillation. The highest activity was shown by ePC in ischemic myocardial reperfusion. The agent suppressed both rapid inward Na+ current and slow inward Ca2+ current. The effects of ePC on transmembrane ion currents suggest that the agent has a unique electrophysiological mechanism of action involving the properties of Classes I and IV antiarrhythmics, making ePC promising in clinical application in patients with impaired conduction and automatism.

Topics: Acute Disease; Animals; Arrhythmias, Cardiac; Cats; Coronary Disease; Myocardial Reperfusion Injury; Phosphocreatine

Oxygen radical toxicity has been implicated in the pathogenesis of myocardial reperfusion injury. In the present study we sought to document the existence of a precise temporal relationship between the time course of free radical generation and the time course of alterations of myocardial energy metabolism during early reperfusion. Rabbit hearts perfused within the bore of a 31-Phosphorous NMR spectrometer were subjected to 30 min of total global ischemia at 37 degrees C. At reflow, 12 control hearts received a bolus of normal perfusate and 12 hearts recombinant human superoxide dismutase (h-SOD) as a 60,000 IU bolus followed by a 100 IU/ml infusion for 15 min. Ischemia resulted in similar depletion of tissue ATP and phosphocreatine (PCr) in the two groups. During the first minute of reflow, recovery of PCr was similar in both groups. However, PCr recovery arrested in control hearts after 2 min, at 63% of baseline, and averaged 64 +/- 4% after 45 min of reperfusion. In contrast, h-SOD treated hearts recovered 86.7% of baseline PCr content after 2 min, 102% after 10 min of reperfusion (P less than 0.001), and 93 +/- 6.4% at the end of the 45 min of reflow (P less than 0.01). The time course of free radical formation during reperfusion was assessed by EPR spectroscopy using both the frozen tissue and the spin trapping methodologies. In control hearts, peak generation of oxygen radicals was reached after 20 s of reflow. h-SOD treatment decreased concentrations of the oxygen-centered radicals in myocardial tissue and of the radical-adducts in the coronary effluent by approximately 80%. Thus, in reperfused hearts peak oxygen radical generation is followed by the occurrence of alterations in the recovery of high energy phosphate metabolism. Both events were largely prevented by administration of h-SOD at reflow. These results provide strong support for a link between oxygen free radical generation and post-ischemic reperfusion injury.

Topics: Adenosine Triphosphate; Analysis of Variance; Animals; Coronary Disease; Energy Metabolism; Female; Free Radicals; Hydrogen-Ion Concentration; Kinetics; Magnetic Resonance Spectroscopy; Myocardial Reperfusion; Myocardium; Oxygen; Phosphates; Phosphocreatine; Rabbits

The effect of 2-(2,5-dimethoxyphenylmethyl)-3-(2-dimethylaminoethyl)- 6-isopropoxy-4(3H)-quinazolinone hydrochloride (MCI-176), a calcium antagonist, on ischemic myocardial metabolism was studied in dog hearts subjected to an occlusion of the left anterior descending coronary artery (LAD) for 3 or 30 min. MCI-176 (0.03 or 0.1 mg/kg), when injected i.v. 5 min before occlusion, increased coronary blood flow and decreased systemic aortic pressure. When the LAD was ligated, the levels of creatine phosphate, ATP, total adenine nucleotides and energy change potential decreased in the ischemic myocardium. Three minutes after ischemia, MCI-176 (0.1 mg/kg) significantly (P less than 0.05) diminished these impairments of energy metabolism. Even 30 min after ischemia, pretreatment with MCI-176 tended to lessen the depletion of ATP and total adenine nucleotides, although these effects were not statistically significant. Myocardial ischemia produced a breakdown of glycogen, an accumulation of lactate, and an inhibition of glycolytic flux through phosphofructokinase reaction. MCI-176 (0.1 mg/kg) significantly (P less than 0.05) reduced these alterations of carbohydrate metabolism after 3 min of ischemia. These results suggest that pretreatment with MCI-176 reduces the impairments of myocardial energy and carbohydrate metabolism in ischemic dog hearts, suggesting that the drug is capable of improving the imbalance between oxygen supply and oxygen demand in the ischemic myocardium.

Topics: Adenine Nucleotides; Adenosine Triphosphate; Animals; Calcium Channel Blockers; Carbohydrate Metabolism; Coronary Disease; Dogs; Energy Metabolism; Female; Heart; Hemodynamics; Male; Myocardium; Phosphocreatine; Phosphofructokinase-1; Quinazolines; Quinazolinones

Using 31P-NMR the existence of Na+/H+ exchange system and its contribution to intracellular pH (pHi) regulation were examined in the isolated isovolumic rat heart under physiological and pathophysiological conditions. Ethylisopropylamiloride (EIPA) was used as a tool to search into the role of Na+/H+ exchange system. In the normal well-oxygenated heart dose-dependent negative chronotropic effects were observed with 10(-6) to 10(-5) M EIPA. After 10(-4) M the heart ceased to beat and a progressive fall of high energy phosphates compounds occurred. However, contrary to expectation pHi did not fall but rose after EIPA. In NH4Cl-loaded hearts removal of NH4Cl resulted in a fall of the pHi followed by a rapid recovery to the normal pHi. After 10(-5) M EIPA the fall of pHi became greater and there was no recovery within 35 min of observation period. This dose of EIPA, however, did not affect the time course of changes in the pHi during 60 min of low-flow ischemia (0.2 ml/min). It is concluded that pHi regulation following an acute acid loading is dependent on amiloride-sensitive Na+/H+ exchange. However, Na+/H+ exchange system does not play an important role in maintenance of the pHi under normoxic or ischemic condition. In the normoxic heart EIPA produced a decrease in heart rate without producing any change either in myocardial energy metabolism or in pHi. Thus, the compound could be categorized as a bradycardic agent.

Topics: Amiloride; Ammonium Chloride; Animals; Blood Pressure; Coronary Disease; Energy Metabolism; Hydrogen-Ion Concentration; In Vitro Techniques; Ion Exchange; Magnetic Resonance Spectroscopy; Male; Myocardium; Perfusion; Phosphocreatine; Rats; Rats, Inbred Strains; Sodium

The effects of regression of left ventricular hypertrophy following atenolol and bunazosin therapy on ischemic cardiac function and myocardial metabolism in spontaneously hypertensive rats (SHR) were studied. Atenolol (50 mg/kg/day) and bunazosin (5 mg/kg/day) were administered to SHR from 19 to 26 weeks of age, whereas tap water was given to control SHR and normotensive Wistar-Kyoto rats (WKY). Both atenolol and bunazosin significantly decreased arterial blood pressure and significantly decelerated the increase in left ventricular weight in SHR. At the end of the long-term treatment, hearts were removed and perfused by the working heart technique for 15 min, and then global ischemia was induced for either 10 or 30 min. The ischemic heart was reperfused for 30 min. The pressure-rate product and the extent of recovery of the coronary flow after reperfusion following 30 min of ischemia in the bunazosin-treated SHR were significantly higher than those in the control SHR and the atenolol-treated SHR. The levels of adenosine triphosphate (ATP), creatine phosphate (CrP), and energy charge potential in the SHR heart reperfused after 30 min of ischemia were significantly lower than those in the reperfused WKY. Both atenolol and bunazosin improved the restoration of ATP and CrP in SHR after reperfusion following 30 min of ischemia. In conclusion, antihypertensive therapy with either atenolol or bunazosin was effective in preventing cardiac hypertrophy and ischemic damage caused by different mechanisms. Factors resulting from stimulation of the cardiac alpha 1 adrenoceptor may play an important role in the development of hypertensive cardiac hypertrophy, just as factors resulting from stimulation of the beta 1-adrenoceptor do.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Atenolol; Blood Pressure; Cardiomegaly; Coronary Circulation; Coronary Disease; Lactates; Lactic Acid; Male; Myocardium; Phosphocreatine; Quinazolines; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Remission Induction

In this work, the technique of 31P-NMR-spectroscopy is applied for the first time to diagnose coronary heart disease in patients, using a suitable measuring technique. In 13 healthy volunteers we applied a method comfortable and tolerable for patients, which enabled us to examine the myocardium inside the reception area of a surface coil. Concerning myocardium-specific selectivity and sensitivity the localization techniques FROGS (Fast-ROtating-Gradient-Spectroscopy), 1-D-ISIS (1-Dimensional-Image-Selected-In-vivo-Spectroscopy) and 3-D-ISIS were compared. By a combination of the 3-D-ISIS-technique with magnetic resonance imaging, we obtained a monitored position of the volume of interest (VOI) within the myocardium, thus gaining a selective measurement. The cube-shaped VOI with a lateral length of 50 mm was placed into the apical-septal area of the myocardium. On the basis of the obtained results, we examined seven patients suffering from coronary heart disease, which was symptomatic and verified by coronary angiography. The 31P-NMR-spectra of the two examined groups were computed into numbers representing the relative content of the myocardial high-energy-phosphates. In addition, the quotients PCr/ATP and Pi/ATP were calculated and compared. With this small number of cases the evaluation of the PCr/ATP-ratios already showed a significant difference of 0.34 (p less than 0.01) between patients with coronary heart disease (0.49 +/- 0.19) and healthy volunteers (0.83 +/- 0.27). The findings suggest the conclusion that 31P-NMR-spectroscopy is able to be instrumental in the diagnostic detection assessment of the metabolic state in coronary heart disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Coronary Disease; Electrocardiography; Energy Metabolism; Humans; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Myocardium; Oxygen Consumption; Phosphates; Phosphocreatine; Reference Values; Signal Processing, Computer-Assisted

The relationships among myocardial ATP, intracellular pH, and ischemic contracture in Langendorff-perfused rat hearts were investigated by 31P nuclear magnetic resonance spectroscopy during total global normothermic ischemia while the left ventricular pressure was recorded continuously via an intraventricular balloon. Glucose-perfused hearts (n = 63) were divided into five groups based on the time of onset of contracture (TOC), and three other groups of hearts were treated to vary the ischemic glycogen availability. ATP levels, which showed no evidence of accelerated ATP depletion during contracture, were significant and variable at TOC. Intracellular pH initially declined and then leveled off at TOC, with lower final pH in hearts with later TOC. We conclude that contracture began when anaerobic glycolysis (and thus glycolytic ATP synthesis) stopped. These results, though consistent with the concept that ischemic contracture in normal hearts results from rigor bond formation due to low ATP levels at the myofibrils, suggest that TOC is more closely related to glycolytic ATP production than to total cellular ATP content, thus providing evidence of some degree of subcellular compartmentation or metabolite channeling. In glycolytically inhibited hearts, the quite early contracture may have a Ca2+ component.

Topics: Anaerobiosis; Animals; Coronary Disease; Glycogen; Glycolysis; Hydrogen-Ion Concentration; In Vitro Techniques; Intracellular Membranes; Magnetic Resonance Spectroscopy; Myocardial Contraction; Myocardium; Phosphocreatine; Phosphorus; Rats; Time Factors

Noninvasive 31P nuclear magnetic resonance measurements indicate that during the initial reperfusion phase myocardial tissue contents of phosphocreatine (PCr) recover rapidly, while ATP levels remain low and recover slowly. There is also a burst of H2O2 during the first 10 min of reperfusion, as indicated by the in vivo inactivation of catalase that occurs only when H2O2, and the inactivator 3-aminotriazole (AMT), are simultaneously present. Neither H2O2 production nor CK inactivation was discernable after ischemia alone. In excitable tissue the PCr and ATP pools are equilibrated by the enzyme creatine kinase (CK), but myocardial CK activity is decreased by 20% after reperfusion, though not by simple washout. Extrapolating from the well-known air sensitivity of CK, we find that limited exposure in vitro to small concentrations of H2O2 can markedly diminish CK activity. We postulate that failure of certain CK isoenzymes at energy-using termini may decouple the relative rates of PCr production and ATP regeneration and hence cause elevated PCr-to-ATP ratios. The assumptions of 1) CK equilibrium during the reperfusion period to calculate free ADP levels and 2) cardiac recovery deduced from the elevation of PCr levels may require reexamination.

Topics: Adenosine Triphosphate; Amitrole; Animals; Catalase; Coronary Disease; Creatine Kinase; Energy Metabolism; Enzyme Activation; Hydrogen Peroxide; Male; Myocardial Reperfusion; Myocardium; Oxygen; Phosphocreatine; Rats; Rats, Inbred Strains

This study determined whether the rapidity of myocardial metabolic and contractile recovery after brief coronary occlusion depends upon the intensity of reactive hyperemia. We also tested the hypothesis that coronary flow rate modulates contractility after brief myocardial ischemia, independent of changes in phosphorus metabolites. Eight open-chest pigs were studied with phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy with 14 s time resolution. After a 29-s anterior descending coronary occlusion, peak Doppler coronary flow velocity was alternately unrestricted (normal hyperemia, 443 +/- 40% of control) or limited to 159 +/- 9% of control. During 29 s coronary occlusion, phosphocreatine-to-inorganic phosphate ratio (PCr/Pi) and systolic segment shortening in the ischemic region fell to 28 +/- 4 and 7 +/- 7% of control, respectively. With normal hyperemia, PCr/Pi and segment shortening recovered within 29 s. With blunted hyperemia, recovery of both parameters was delayed an additional 29-43 s, associated with reduced subendocardial blood flow (measured with radioactive microspheres) and persistent intracellular acidosis. However, the relationship between segment shortening and PCr/Pi was unaffected by the intensity of reactive hyperemia. Thus blunted reactive hyperemia significantly delays metabolic and contractile recovery from brief ischemia, probably via transient maldistribution of transmural perfusion. However, coronary blood flow rate does not independently modulate contractility after brief reversible ischemia.

Topics: Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Coronary Vessels; Energy Metabolism; Female; Heart; Hyperemia; Magnetic Resonance Spectroscopy; Myocardium; Phosphates; Phosphocreatine; Reperfusion; Swine; Systole; Time Factors

The effect of thoracic epidural anesthesia (TEA) on the ischemic myocardium was examined in open-chest dogs anesthetized intravenously. Ischemia induced by brief coronary artery occlusion caused an elevation of the ST segment in epicardial ECG and a reduction in myocardial pH and contractile force. TEA with 0.15 ml/kg of 0.4% bupivacaine solution attenuated an ischemia-induced decrease in myocardial pH and an increase of the ST segment in epicardial ECG. This attenuation was maintained even after the restoration of blood pressure and heart rate, which had been decreased significantly after TEA, to pre-TEA levels, suggesting that a beneficial effect of TEA should not be confined to its hemodynamic changes such as decreased blood pressure and heart rate. In contrast, the subendocardial contents of ATP, creatine phosphate (CP) and lactate were not affected by TEA, either in the presence or the absence of 5 min LAD occlusion. These results suggest that neither hemodynamic nor metabolic changes are responsible for the reduced myocardial ischemic acidosis induced by TEA after brief coronary artery occlusion. The acidosis-saving property of TEA is favorable for the ischemic heart.

Topics: Adenosine Triphosphate; Anesthesia, Epidural; Animals; Bupivacaine; Coronary Disease; Dogs; Female; Hydrogen-Ion Concentration; Lactates; Male; Myocardial Contraction; Myocardium; Phosphocreatine; Thoracic Vertebrae

Ischemic preconditioning slows ATP depletion and ultrastructural damage during the final episode of ischemia. To define the influence of creatine phosphate (CP) and intracellular pH (pHi) on this effect, CP and pHi were serially measured in porcine hearts without collateral circulation by using 31P-NMR spectroscopy and ultrastructural examination.. Farm pigs weighing 12-15 kg were anesthetized with Fluothane. The control group underwent a single occlusion (20 minutes or 60 minutes); the preconditioned group underwent four episodes of 5-minute occlusion and 5-minute reperfusion followed by a sustained occlusion (20 minutes or 60 minutes). After ischemic preconditioning, CP increased to 115 +/- 11% (p less than 0.05) of preischemic value and ATP decreased to 84 +/- 8% (p less than 0.05) of preischemic value, but pHi returned to preischemic value. At 5 and 10 minutes of sustained ischemia, CP was significantly preserved in the preconditioned group (control group, 19 +/- 3% versus preconditioned group, 29 +/- 4% at 5 minutes; control group, 5 +/- 3% versus preconditioned group, 11 +/- 3% at 10 minutes; p less than 0.05). At 15 and 20 minutes of sustained ischemia, ATP was significantly preserved in the preconditioned group (control group, 64 +/- 3% versus preconditioned group, 73 +/- 3% at 15 minutes; control group, 51 +/- 7% versus preconditioned group, 62 +/- 2% at 20 minutes; p less than 0.05). At 10, 15, 20, and 25 minutes of sustained ischemia, pHi was significantly higher in the preconditioned group (control group, 6.5 +/- 0.05 versus preconditioned group, 6.7 +/- 0.1 at 10 minutes; control group, 6.3 +/- 0.05 versus preconditioned group, 6.6 +/- 0.06 at 15 minutes; control group, 6.1 +/- 0.1 versus preconditioned group, 6.4 +/- 0.1 at 20 minutes; control group, 6.0 +/- 0.2 versus preconditioned group, 6.3 +/- 0.1 at 25 minutes; p less than 0.05). Ultrastructural changes were milder in the preconditioned group at 20 minutes of sustained ischemia.. In addition to ATP and ultrastructure, preconditioning preserved CP and pHi during sustained ischemia. These protective effects might be due to overshoot phenomenon of CP and/or reduced ATP consumption. The relatively longer period of preservation of pHi, which probably is the result of reduced ATP consumption, indicates its greater contribution to reducing infarct size than that of CP and ATP.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Myocardial Infarction; Myocardium; Phosphates; Phosphocreatine; Swine

Severe arrhythmias occur predictably on reperfusion after 5 minutes of coronary occlusion in the rat. There is little data available on whether ischemic preconditioning (PC) of hearts can reduce the incidence of such arrhythmias. The effect of PC (three cycles of 2 minutes of coronary occlusion and 5 minutes of reperfusion) on development of arrhythmias after a subsequent 5-minute coronary artery occlusion and reperfusion was studied. Rats (n = 16 each group) underwent 5-minute occlusion and reperfusion alone or preceded by PC; arrhythmias were monitored during ischemia and for 10 minutes of reperfusion, and biopsies were taken for creatine phosphate and adenosine triphosphate in ischemic and nonischemic zones of the left ventricle. PC reduced the incidence of ventricular tachycardia (VT) during occlusion (81% control versus 13% PC, p less than 0.001). On subsequent reperfusion, ventricular fibrillation (VF) developed in zero PC animals versus 13 (81%) of controls (p less than 0.001), and irreversible VF in zero of PC versus seven (44%) of controls (p = 0.007). VT occurred in four (25%) of PC versus all (100%) of controls (p less than 0.001). PC reduced mean duration of VT plus VF from 320 +/- 54 to 5 +/- 1 seconds (p less than 0.001) and delayed arrhythmia onset from 8 +/- 2 to 85 +/- 35 seconds after reperfusion. There was no difference in creatine phosphate levels in the ischemic zone at the end of reperfusion in PC animals compared with controls without irreversible VF (16.2 +/- 4.1 versus 15.5 +/- 3.9 nmol/mg protein, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Female; Myocardial Reperfusion Injury; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains; Tachycardia, Supraventricular

The effect of adenosine receptor antagonism on function and metabolism was examined in isolated hearts during low flow ischemia and reperfusion. Isovolumic rat hearts perfused at constant flow were subjected to 30 min of ischemia followed by 30 min of reperfusion. Infusion of vehicle or 10 microM 8-phenyltheophylline (8-PT) was initiated 10 min before ischemia and maintained throughout reperfusion. 8-PT infusion had no significant effects on hemodynamic parameters or metabolism preischemia. During ischemia, left ventricular developed pressure declined to approximately 15% of preischemic values in control and 8-PT hearts, and ATP and PCr decreased to approximately 73 and 60% of preischemic values. Inorganic phosphate (Pi) increased to 353 = 41 and 424 +/- 53% of preischemic values in control and 8-PT hearts, respectively. After reperfusion, function recovered to greater than 95% of preischemic levels in control and 8-PT hearts. Unlike control hearts, recovery of metabolites was significantly different during reperfusion in 8-PT hearts (P less than 0.05); ATP, phosphocreatine, and Pi recovered to 82 +/- 8, 71 +/- 8, and 281 +/- 27% of preischemic values, respectively. Venous purine washout was significantly greater (P less than 0.05) during reperfusion in 8-PT hearts (327 +/- 113 nmol) than in control hearts (127 +/- 28 nmol). Blockade of adenosine receptors appears to adversely affect metabolic but not functional recovery in the ischemic-reperfused myocardium.

Topics: Adenosine; Adenosine Triphosphate; Animals; Coronary Disease; Heart; Hemodynamics; Male; Myocardium; Phosphates; Phosphocreatine; Rats; Rats, Inbred Strains; Receptors, Purinergic; Reperfusion Injury; Theophylline

Topics: Adenosine Triphosphate; Coronary Disease; Humans; Myocardium; Phosphocreatine

Using an isolated perfused heart preparation of the rat, the effects of lidocaine (Na+ channel blocker) on ischemic derangements of the mechanical function and energy metabolism of the ventricular myocardium were studied. The myocardial tissue levels of creatine phosphate (CP), ATP, inorganic phosphate (PI) and pH were determined using 31P-NMR. Global ischemia was induced by cross-clamping the aortic inflow line for 20 min, which resulted in a fall in CP, ATP, and pH, and a rise in Pi. The test hearts were perfused with a lidocaine-containing solution (10(-7) M) for 20 min prior to the induction of global ischemia and for 80 min after reperfusion. No significant decline of the myocardial mechanical function expressed as "left ventricular pressure x heart rate" was observed in lidocaine-treated hearts. Lidocaine significantly suppressed the fall in the myocardial ATP and pH during ischemia. Furthermore, in the reperfusion phase, restoration of high ATP levels was observed with the lidocaine-treated heart. These results manifest the beneficial effect of lidocaine on ischemia-induced cell injury.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Energy Metabolism; Hemodynamics; Hydrogen-Ion Concentration; In Vitro Techniques; Lidocaine; Magnetic Resonance Spectroscopy; Perfusion; Phosphocreatine; Rats; Rats, Inbred WKY

The effect of human superoxide dismutase (h-SOD) on the ischemic heart was studied in the isolated perfused working rat heart. Myocardial mechanical function expressed as pressure-rate product decreased and completely stopped within 5 min after the onset of global ischemia, and never recovered after reperfusion following 20 min of ischemia. In the ischemic myocardium, the levels of ATP, ADP, and creatine phosphate decreased, and those of AMP and lactate increased. Reperfusion of the ischemic heart did not restore the level of ATP completely. When the heart was treated with h-SOD, the perfusion medium was switched from the buffer containing no h-SOD to that containing h-SOD at either 100, 300 or 1,000 units/ml 5 min before the onset of ischemia. The pressure-rate products of the heart treated with 100, 300, and 1,000 units/ml of h-SOD were restored by reperfusion to 22%, 59%, and 51% of the preischemic level, respectively. The levels of ATP and creatine phosphate in the reperfused heart with 300 and 1,000 units/ml of h-SOD were significantly higher than those without h-SOD. However, a dose-response relationship was not observed when h-SOD was used in concentrations greater than 300 units/ml. These results indicate that a certain amount of h-SOD has some beneficial effects on the ischemic myocardium.

Topics: Adenine Nucleotides; Animals; Coronary Disease; Heart; Humans; In Vitro Techniques; Lactates; Male; Myocardial Reperfusion; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains; Superoxide Dismutase

The mechanism responsible for heterogeneity in tissue pH was investigated in perfused rat hearts subjected to ischemia/reperfusion insult, by correlating the time course of pH changes to the severity of vascular impairment. In 25 perfused hearts, myocardial pH was monitored by 31 P-NMR spectra. During ischemia, pH, which was 7.1 at the beginning of ischemia, progressively decreased and reached a steady level of 5.9 (5.9-compartment) after 40 minutes. In addition, another define peak of pH 7.1 (7.1-compartment) became evident after 50 min of ischemia. The 7.1-compartment grew higher with ischemic time and was only observed after 180 min of ischemia. Although reperfusion after 20 min of ischemia recovered pH, ATP, and creatine phosphate, reperfusion after 50 min left two Pi peaks, the 5.9- and 7.1-compartments; the former gradually decreased with a concomitant increase of the latter. Reperfusion after 180 min of ischemia with various pH levels did not shift the Pi peak from pH 7.1, suggesting that the perfusate did not reach that compartment, the impaired flow region. High coronary resistance and a heterogeneous staining pattern concomitant with a late appearance of the 7.1 component further supported this hypothesis. Myocardial coenzyme Q10 radical, an indicator of the tissue redox state, was also low in those hearts which were reperfused after 50 min of ischemia. Thus, the splitting of the Pi peak, caused by reperfusion after prolonged ischemia, represents the existence of a no-reflow region.

Topics: Animals; Coenzymes; Coronary Disease; Coronary Vessels; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Male; Myocardial Reperfusion Injury; Myocardium; Oxidation-Reduction; Phosphocreatine; Rats; Rats, Inbred Strains; Ubiquinone; Vascular Resistance

To investigate the high-energy phosphate metabolic correlates of left ventricular (LV) dysfunction during the onset and recovery from severe, global myocardial ischemia in vivo, seven preinstrumented closed-chest dogs had ECG-gated phosphorus-31 (31P) NMR-spectroscopy (NMR-S) studies performed and LV micromanometer and sonomicrometer data measured before, during, and every 5 min following severe occlusive global myocardial ischemia. Ischemic LV + dP/dtmax fell from 2396 +/- 576 mm Hg/s at baseline to 2185 +/- 478 mm Hg/s (p less than 0.05) and did not normalize until after 30 min of reperfusion. LV ejection fraction (EF) decreased significantly (0.32 +/- 0.07 EF units to 0.12 +/- 0.13 EF units; p less than 0.05) and did not recover by 30 min of reperfusion (0.27 +/- 0.09 units; P less than 0.05 vs baseline). Simultaneous 31P NMR-S studies demonstrated excellent beta-ATP signal-to-noise (10 +/- 4:1). Myocardial acidosis occurred during global ischemia (delta pH = -0.22 +/- 0.23 units; p less than 0.05), with recovery at 30 min of reperfusion. Inorganic phosphate/phosphocreatine ratio (Pi/PCr) increased significantly during ischemia (0.46 +/- 0.07 to 0.61 +/- 0.07; P less than 0.05), with delayed normalization of this ratio at 30 min of reperfusion. beta-ATP peak area did not change during ischemia. Pi/PCr and LV contractility (+dP/dtmax) were significantly correlated at baseline (r = -0.70) and during global ischemia (r = -0.78; p less than 0.01), but not during recovery (r = 0.006; p = NS). Therefore, the simultaneous evaluation of high-fidelity hemodynamic data and topical 31P NMR-S can be performed in the intact state.

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Coronary Circulation; Coronary Disease; Dogs; Heart; Magnetic Resonance Spectroscopy; Myocardial Reperfusion; Myocardium; Oxygen Consumption; Phosphocreatine; Phosphorus; Stroke Volume; Ventricular Function, Left

Effects of amiodarone injected intravenously (i.v.) at two doses (10 and 20 mg/kg) on perfused isovolumic rat hearts were assessed by P-31 nuclear magnetic resonance (NMR). P-31 NMR is used to measure intracellular myocardial pH, phosphocreatine (PCr), and ATP contents time evolutions. Myocardial mechanical function is estimated by heart rate (HR), left ventricular developed pressure (LVP), and coronary flow (CF). In experimental procedure A (2-h retrograde perfusion), drug injection induced a dose-dependent bradycardia (10-20%) and a slight decrease in LVP but did not affect CF, pH, PCr, or ATP contents. Experimental procedure B consisted of 30-min stabilization, 18-min ischemia, and 72-min reperfusion. During ischemia, amiodarone did not preserve ATP and PCr pools and did not alleviate acidosis. ATP decreased to 30% of its control values, whereas the PCr peak was hardly detectable after 12 min of ischemia. After 24 min of reflow, HR, PCr, and pH of treated hearts recovered. LVP recovered after 36 min, whereas for control hearts, HR, PCr, and pH recovered after 42 min and LVP did not reach its control values at the end of reperfusion time. Faster pH recovery is explained by a preservation of Na+/K+ ATPase due to the influence of amiodarone on membrane lipid dynamics.

Topics: Adenosine Triphosphate; Amiodarone; Animals; Blood Pressure; Coronary Circulation; Coronary Disease; Heart Rate; Hydrogen-Ion Concentration; In Vitro Techniques; Magnetic Resonance Spectroscopy; Male; Myocardial Reperfusion; Myocardium; Phosphocreatine; Phosphorus Isotopes; Rats

To examine the effects of nipradilol on ischemic myocardium, experiments were performed on regional myocardial blood flow (MBF) and energy metabolism in anesthetized, open-chest dogs. Nipradilol at a dose of 0.3 mg/kg was i.v.-administered 10 min after coronary ligation. MBFs at various sites, including ischemic and non-ischemic areas, were determined by the hydrogen gas clearance method. The levels of ATP and creatine phosphate (CP) at the site of MBF determination were measured 60 min after ligation, and mitochondrial function (RCI, QO2) in the ischemic and non-ischemic areas was determined. Following nipradilol administration, aortic pressure and heart rate were significantly lowered. In ischemic areas with MBF below 40 ml/min/100 g, nipradilol had no influence on MBF. However, the tissue level of ATP in nipradilol treated hearts was significantly higher as compared with untreated hearts. In the area of mild ischemia with MBF of 40-60 ml/min/100 g, nipradilol preserved the tissue ATP and CP levels in spite of a decrease in MBF. Moreover, an inhibition of the decrease in mitochondrial respiratory function was observed in ischemic areas with MBF below 20 ml/min/100 g. Thus, nipradilol administered following ischemia preserved ATP content and mitochondrial function in the ischemic myocardium with reduction of heart rate and aortic pressure. This suggests that nipradilol exerts a cardioprotective effect in acute ischemia. It seems that the cardioprotective effect is due to a decrease in myocardial oxygen demand and preservation of mitochondrial function.

Topics: Adenosine Triphosphate; Adrenergic beta-Antagonists; Animals; Blood Pressure; Coronary Circulation; Coronary Disease; Dogs; Energy Metabolism; Heart; Heart Rate; In Vitro Techniques; Mitochondria, Heart; Myocardium; Oxygen Consumption; Phosphocreatine; Propanolamines

Effects of a selective alpha 1-adrenergic blocking agent, bunazosin, on myocardial energy metabolism in the ischemic heart were studied. Ischemia was induced by ligating the left anterior descending coronary artery of the dog heart. Bunazosin was injected intravenously either 5 or 20 min before coronary artery ligation. Hearts were removed 3 min after coronary ligation and used for determination of the levels of cardiac tissue metabolites. Ischemia decreased the levels of ATP, creatine phosphate, glycogen and glucose, and increased the levels of ADP, AMP, hexose monophosphates and lactate. The energy charge potential (ECP) calculated was decreased by ischemia. Pretreatment with bunazosin inhibited the decrease in ATP and the increase in AMP caused by ischemia, resulting in the high value of ECP in the ischemic myocardium. Bunazosin also prevented the changes in carbohydrate metabolism caused by ischemia. It is concluded that bunazosin may reduce the influence of ischemia on the myocardium.

Topics: Adenine Nucleotides; Adrenergic alpha-Antagonists; Animals; Carbohydrate Metabolism; Coronary Disease; Dogs; Electrocardiography; Energy Metabolism; Female; Heart; Hemodynamics; Hexosephosphates; In Vitro Techniques; Lactates; Male; Myocardium; Phosphocreatine; Pyruvates; Quinazolines

The effect of nipradilol, a newly developed beta-adrenoceptor blocking agent with a vasodilatory action, on myocardial energy metabolism has been examined in the dog ischaemic heart, and compared with that of propranolol. Ischaemia was induced by ligating the left anterior descending coronary artery. Either saline, nipradilol (0.3 mg kg-1), or propranolol (1 mg kg-1) was injected intravenously 5 min before coronary ligation. After 3 or 30 min of coronary ligation, the ischaemic region of the myocardium was removed, and the endocardial portion used to determine the levels of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), creatine phosphate (CrP) and lactate. Ischaemia decreased the levels of ATP and CrP, and increased the levels of ADP, AMP and lactate. Immediately after the injection of nipradilol, rapid falls in blood pressure and heart rate were observed. Pretreatment with nipradilol lessened the decreases in the levels of ATP and CrP and the increases in the levels of AMP and lactate, caused by 3 min of ischaemia, to the same extent as propranolol. However, after 30 min of ischaemia, nipradilol had no effect on myocardial metabolism unlike propranolol. These results indicate that nipradilol can reduce ischaemic influences on myocardial metabolism as well as propranolol, but only in the early stages of ischaemia.

Topics: Adenine Nucleotides; Adrenergic beta-Antagonists; Animals; Blood Pressure; Coronary Circulation; Coronary Disease; Dogs; Energy Metabolism; Female; Heart; Heart Rate; Lactates; Male; Myocardium; Phosphocreatine; Propanolamines

The electrophysiologic effects of phosphocreatine were assessed in isolated, superfused guinea pig ventricular tissues to gain an insight into its purported antiarrhythmic properties. Under normal conditions, 10 mM phosphocreatine significantly increased effective refractory period by 14.0 +/- 0.4%, but under ischemic-like conditions (hypoxia, hyperkalemia, acidosis) it showed no significant effect. Moreover, phosphocreatine reduced free [Ca2+]0 by nearly 20% and the changes induced by this compound in control tissues could be largely reproduced with an altered Tyrode's solution containing less than 0.6 mM Ca2+. The experiments suggest that phosphocreatine may act in a similar manner as class III antiarrhythmic agents on non-ischemic, normal tissue by mechanisms related in part to changes in extracellular Ca2+ composition.

Topics: Action Potentials; Animals; Anti-Arrhythmia Agents; Coronary Disease; Disease Models, Animal; Guinea Pigs; Heart Ventricles; In Vitro Techniques; Models, Cardiovascular; Myocardium; Phosphocreatine; Purkinje Fibers; Ventricular Function

The pathogenesis of post-ischaemic depression of contractility in myocardium was examined in isovolumic rat heart. 31P-NMR was used to monitor changes in ATP, creatine phosphate (CrP), inorganic phosphate (Pi), and [H+] during brief periods of ischaemia and reperfusion with and without allopurinol treatment. During 5, 10, or 15 min of total global ischaemia, the decline in function (rate-pressure product) correlated inversely with [Pi] (r = 0.92, P less than 0.01). Cardiac function exhibited a slow progressive recovery during 20 min of reperfusion, ultimately reaching only 85%, 78%, and 69% of its pre-ischaemic value following 5, 10, and 15 min of global ischaemia respectively. Following each ischaemic period [ATP], [CrP], [Pi], and [H+] all recovered to control levels within 5-10 min of initiating reperfusion. Allopurinol (2 mM) treatment of hearts made ischaemic for 15 min significantly improved contractile recovery to 89 +/- 7%. Allopurinol also exhibited significant anti-arrhythmic activity during the reperfusion period, decreasing the incidence of premature contractions and the duration of tachy-arrhythmias. Allopurinol had no effect on the final repletion of [ATP] and [CrP], or the recovery of [Pi] and [H+], although the rate of ATP repletion was elevated in the initial 5 min of reperfusion. These results show that neither depletion of the cytosolic high-energy phosphate pool, nor sustained elevations in [Pi] or [H+] are important in the production of post-ischaemic contractile impairment. The beneficial action of allopurinol suggests that xanthine oxidase derived oxygen free-radicals may be involved in the sustained contractile dysfunction following brief ischaemic episodes.

Topics: Adenosine Triphosphate; Allopurinol; Animals; Arrhythmias, Cardiac; Coronary Disease; Energy Metabolism; In Vitro Techniques; Male; Myocardial Contraction; Myocardial Reperfusion Injury; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains

The effect of cooling to 25 degrees C on myocardial metabolism was studied during four periods of global ischemia (10 minutes each) followed by 15 minutes of reperfusion in dogs on cardiopulmonary bypass. Systemic and heart temperature at normothermia (group N, 34 degrees C; n = 15) was compared with general hypothermia (group H, 25 degrees C; n = 16). Before and at the end of each aortic crossclamp period in small myocardial biopsy specimens the adenosine triphosphate, creatine phosphate, inorganic phosphate, glycogen, and lactate content was analyzed. Also, lactate and inorganic phosphate were measured in the coronary effluents during the repetitive periods of reperfusion. Hemodynamic function was not different at 60 minutes after cardiopulmonary bypass compared with pre-cardiopulmonary bypass values, and was not different between the groups N and H. The tissue content of adenosine triphosphate and glycogen decreased progressively during the experimental period, resulting in slightly depressed values in both groups at the end of cardiopulmonary bypass. Pronounced effects of ischemia and reperfusion on tissue content of creatine phosphate, inorganic phosphate, and lactate were observed after each period of ischemia. The net decrease in tissue creatine phosphate content was not different between groups N and H (41 +/- 4 versus 38 +/- 4 mumol.gm-1 dry weight; mean +/- standard error of the mean) after 10 minutes of ischemia. However, during ischemia the net inorganic phosphate increase in myocardial tissue was significantly higher in group H (70 +/- 7 mumol.gm-1) than in group N (44 +/- 3 mumol.gm-1). These findings do not support the notion that myocardial protection is improved during hypothermia. Moreover, quantitatively the release of inorganic phosphate and lactate did not correlate with the amount accumulated in the myocardial tissue during the preceding periods of ischemia. The release appeared to be temperature dependent, that is, significantly reduced at 25 degrees C. The present data demonstrate why clinical outcome is satisfactory in both surgical procedures, when in general the periods of aortic crossclamping do not exceed 10 minutes each and the reperfusion periods in between the ischemic episodes last about 15 minutes. Besides, the findings indicate that hypothermia is not strictly necessary under these circumstances.

Topics: Adenosine Triphosphate; Animals; Aorta; Cardiopulmonary Bypass; Constriction; Coronary Disease; Dogs; Glucose; Lactates; Myocardium; Phosphocreatine; Temperature

The time course of changes in the myocardial levels of nonesterified fatty acids (NEFA), adenosine triphosphate (ATP), creatine phosphate (CrP) and lactate, and those in the cardiac mechanical function during ischemia and reperfusion was investigated in the isolated, perfused, working rat heart. Ischemia was produced by lowering the afterload pressure from 60 to 0 mm Hg, and reperfusion resulted from raising the afterload pressure to 60 mm Hg. Ischemia stopped the heart beat, and increased the myocardial levels of unsaturated NEFA (such as arachidonic, palmitoleic, and linoleic acids) as a function of the ischemic period; it decreased the myocardial levels of ATP and CrP, and increased the myocardial level of lactate. The level of arachidonic acid increased when the myocardial level of ATP fell below 5 mumol/g dry weight. Reperfusion after ischemia started the heart beat, and restored the mechanical function which depended on the preceding ischemic period. Reperfusion also increased the levels of ATP and CrP and decreased the level of lactate, whereas it further increased the levels of the NEFA that had been elevated by ischemia. The recovery of mechanical function was inversely correlated with the myocardial level of arachidonic acid during ischemia and reperfusion. We concluded that changes in the myocardial levels of NEFA during ischemia and reperfusion are different from those of ATP, CrP, and lactate, and suggest that the myocardial level of arachidonic acid during ischemia and reperfusion can be a sensitive and suitable marker for the recovery of mechanical function during reperfusion.

Topics: Adenosine Triphosphate; Animals; Arachidonic Acid; Arachidonic Acids; Coronary Disease; Fatty Acids, Nonesterified; Heart; Lactates; Lactic Acid; Male; Myocardial Reperfusion; Myocardium; Perfusion; Phosphocreatine; Rats; Rats, Inbred Strains; Time Factors

The effects of long-term treatment with diltiazem on the heart in normotensive (WKY) and spontaneously hypertensive rats (SHR) were studied. Diltiazem was added to the drinking fluid (900 mg/liter) and given ad libitum from 19 to 26 weeks of age, whereas tap water was given to the control animals. Although diltiazem did not decrease blood pressure in SHR, it decelerated the increase in their left ventricular weight (p less than 0.01). Hearts were removed and perfused by the working heart technique for 15 min, and then global ischemia was induced for either 10 or 30 min. The ischemic heart was reperfused for 30 min. The extent of recovery of coronary flow after reperfusion, following 30 min of ischemia in the diltiazem-treated SHR, was higher than that in the control SHR (p less than 0.01). The levels of adenosine triphosphate (ATP), creatine phosphate (CrP), and energy charge potential in the SHR heart reperfused after 30 min of ischemia were lower than those in the reperfused WKY heart (p less than 0.01, respectively). Diltiazem improved the restoration of ATP and CrP and prevented the decrease in energy charge potential in SHR after reperfusion following 30 min of ischemia (p less than 0.01, respectively). In conclusion, long-term treatment of SHR with diltiazem may protect the myocardium when myocardial ischemia occurs.

Topics: Adenine Nucleotides; Animals; Blood Pressure; Cardiomegaly; Coronary Circulation; Coronary Disease; Diltiazem; Energy Metabolism; Heart; Hypertension; In Vitro Techniques; Male; Myocardium; Perfusion; Phosphocreatine; Rats; Rats, Inbred SHR; Rats, Inbred WKY

Ultrastructural changes in normal and hypertrophied dog hearts under conditions of total ischemia were studied by electron microscope method. In the control group sings of irreversible damage appeared in 90 min, in the presence of phosphocreatine, 10 mM, these changes became apparent in 120 min. In the hypertrophied hearts signs of the irreversible damages became evident in 60 and 90 min in the absence and presence of phosphocreatine, respectively. Ability of phosphocreatine to protect both normal and hypertrophied myocardium allows to use it safely.

Topics: Animals; Cardiomegaly; Cardioplegic Solutions; Coronary Disease; Dogs; Heart; Heart Arrest, Induced; Microscopy, Electron; Myocardium; Phosphocreatine; Time Factors

Isolated working rat hearts were subjected to 20 min of global ischaemia and either 5 min or 15 min of reperfusion. The subcellular distribution of ATP, ADP, AMP, phosphocreatine and Pi were determined before and after ischaemia by the method of non-aqueous tissue fractionation. Ventricular function and the cytosolic, mitochondrial and ATPase-associated compartmentation of metabolites were measured. After 5 min of reperfusion, only 13 +/- 9% of the pre-ischaemic contractile function was restored compared to 67 +/- 8% after 15 min reperfusion. ATP was reduced in all cellular compartments after 5 min of reperfusion but was only decreased from pre-ischaemic values in the cytosolic compartment after 15 min of reperfusion (17.1 +/- 3.9 nmol/mg vs. 4.3 +/- 1.5 nmol/mg total protein; P less than 0.05). The mitochondrial [ATP]/[ADP] was reduced from a normal value of 4.36 to 1.79 after 5 min but recovered to 4.62 after 15 min of reperfusion. Most of the Pi was located in the mitochondria or with the ATPase fraction of the cell, with only 16% of the total Pi free in the cytosol. This study indicates that the capacity of the heart to recover function may be compromised during early reperfusion by a 59% increase in mitochondrial phosphate content and during late reperfusion by a reduced cytosolic/mitochondrial concentration ratio of both ATP (from 0.85 to 0.19) and phosphocreatine (from 3.9 to 1.24).

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphatases; Adenosine Triphosphate; Animals; Coronary Disease; Cytosol; Energy Metabolism; Male; Mitochondria, Heart; Myocardial Contraction; Myocardial Reperfusion; Myocardium; Phosphates; Phosphocreatine; Rats; Rats, Inbred Strains; Subcellular Fractions

The purpose of this study was to compare the degree of ischemic and hypoxic injury in normal versus hypertrophied rat hearts to investigate basic mechanisms responsible for irreversible myocardial ischemic injury. Hearts from rats with bands placed on the aortic arch at 23 days of age (BAND) and sham-operated rats (SHAM, 8 weeks postoperative) were isolated, perfused with Krebs buffer, and had a left ventricular balloon to measure developed pressure. Hearts were made globally ischemic until they developed peak ischemic contracture and were reperfused for 30 minutes. Additional hearts were perfused for 15 minutes with glucose-free hypoxic buffer followed by 20 minutes of oxygenated perfusion. There was an 87% increase in heart weight of BAND compared with SHAM (p less than 0.01). During ischemia, lactate levels increased faster in BAND compared with SHAM, ischemic contracture occurred earlier in BAND than in SHAM despite no difference in ATP levels, and postischemic recovery of left ventricular pressure was less in BAND (26.8 +/- 5.6% of control left ventricular pressure, mean +/- SEM) compared with SHAM (40 +/- 4.6%, p less than 0.05). During hypoxic perfusion, lactate release was greater in BAND than in SHAM (48.8 +/- 1.2 versus 26.6 +/- 0.97 mumols/g, p less than 0.01), and with reoxygenation, lactate dehydrogenase release was less in BAND than in SHAM (13.2 +/- 0.7 versus 19.5 +/- 0.2 IU/g, p less than 0.01). After hypoxia and reoxygenation, left ventricular pressure recovery was greater in BAND than in SHAM (93 +/- 8.4% versus 66 +/- 5.3%, p less than 0.01). Thus, this study suggests that hypertrophied hearts have a greater potential for glycolytic metabolism, resulting in an increased rate of by-product accumulation during ischemia, which may be responsible for the increased susceptibility of hypertrophied hearts to ischemic injury.

Topics: Adenosine Triphosphate; Animals; Aorta; Cardiomegaly; Constriction; Coronary Disease; Glycogen; Heart Ventricles; Hypoxia; Lactates; Lactic Acid; Male; Microscopy, Electron; Myocardial Contraction; Myocardium; Phosphocreatine; Pressure; Rats; Rats, Inbred Strains

The relevance of radical formation in disturbances of energy metabolism in the postischemic heart is not clear. This study provides the first evidence of a significant correlation between the amount of oxy-radicals trapped in the effluent of isolated hearts upon reperfusion and the decreased myocardial content of phosphocreatine and ATP. This suggests that the loss of high-energy compounds might contribute to oxy-radical production during reperfusion. The application of ESR spin trapping and of NMR technique to the same heart is a new approach to investigate the pathobiochemical relevance of free radicals for the heart muscle.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Electron Spin Resonance Spectroscopy; Female; Free Radicals; Kinetics; Magnetic Resonance Spectroscopy; Myocardial Reperfusion; Phosphocreatine; Rats; Rats, Inbred Strains

We have previously demonstrated that induction of the heat-shock response in rats results in improved recovery of isolated Langendorff-perfused rat hearts subjected to low-flow ischemia followed by reperfusion (Currie et al., 1988). The mechanisms underlying this protective effect of heat-shock are uncertain although the protection was associated with enhanced content of the antioxidant enzyme catalase but not superoxide dismutase or glutathione peroxidase (Currie et al., 1988). Various investigators have suggested the importance of improved energy metabolism in determining recovery following ischemia (Pasque and Wechsler, 1984; Haas et al., 1984; Devous and Lewandowski, 1987). We therefore examined, using a working rat heart model subjected to 10 or 15 min zero flow ischemia whether changes in energy metabolites could account for the protective effect of the heat-shock response. Hearts perfused 24 h after induction of heat-shock failed to demonstrate significant improvement of recovery following 10 min ischemia, however recovery was significantly enhanced in hearts reperfused after 15 min ischemia. Ischemia produced a depression in both ATP and creatine phosphate (CP) content whereas a moderate elevation in ADP and AMP and a marked increase in tissue lactate were evident. These changes were unaffected by prior heat-shock treatment. For both durations of ischemia tissue metabolites were determined during early (5 min) and late (30 min) reperfusion. Although partial recovery in high energy phosphates and a return of ADP, AMP and lactate to near-normal levels were evident, no differences in energy products were observed between hearts from normal or heat-shocked animals, in spite of significantly enhanced recovery.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Coronary Disease; Energy Metabolism; Heart Ventricles; Hot Temperature; Lactates; Male; Phosphocreatine; Physical Exertion; Rats; Rats, Inbred Strains; Ventricular Function

The maintenance of cellular levels of high-energy phosphates is required for myocardial function and preservation. In animals, severe myocardial ischemia is characterized by the rapid loss of phosphocreatine and a decrease in the ratio of phosphocreatine to ATP.. To determine whether ischemic metabolic changes are detectable in humans, we recorded spatially localized phosphorus-31 nuclear-magnetic-resonance (31P NMR) spectra from the anterior myocardium before, during, and after isometric hand-grip exercise.. The mean (+/- SD) ratio of phosphocreatine to ATP in the left ventricular wall when subjects were at rest was 1.72 +/- 0.15 in normal subjects (n = 11) and 1.59 +/- 0.31 in patients with nonischemic heart disease (n = 9), and the ratio did not change during hand-grip exercise in either group. However, in patients with coronary heart disease and ischemia due to severe stenosis (greater than or equal to 70 percent) of the left anterior descending or left main coronary arteries (n = 16), the ratio decreased from 1.45 +/- 0.31 at rest to 0.91 +/- 0.24 during exercise (P less than 0.001) and recovered to 1.27 +/- 0.38 two minutes after exercise. Only three patients with coronary heart disease had clinical symptoms of ischemia during exercise. Repeat exercise testing in five patients after revascularization yielded values of 1.60 +/- 0.20 at rest and 1.62 +/- 0.18 during exercise (P not significant), as compared with 1.51 +/- 0.19 at rest and 1.02 +/- 0.26 during exercise before revascularization (P less than 0.02).. The decrease in the ratio of phosphocreatine to ATP during hand-grip exercise in patients with myocardial ischemia reflects a transient imbalance between oxygen supply and demand in myocardium with compromised blood flow. Exercise testing with 31P NMR is a useful method of assessing the effect of ischemia on myocardial metabolism of high-energy phosphates and of monitoring the response to treatment.

Topics: Adenosine Triphosphate; Adult; Aged; Coronary Disease; Exercise; Female; Humans; Magnetic Resonance Spectroscopy; Male; Middle Aged; Myocardium; Oxygen Consumption; Phosphocreatine

The effects of 1 hour of mild and moderate reductions in coronary blood flow on myocardial high-energy phosphate levels were evaluated. Thirty anesthetized pigs were instrumented with left anterior descending arterial and venous catheters, crystals for instantaneous wall thickness, and a fluid-filled occluder. Measurement of myocardial blood flow was performed with microspheres, and a series of myocardial biopsies also was performed. In 10 pigs, overall coronary blood flow was lowered by 22%, with a fall in subendocardial-to-subepicardial flow ratio from 1.11 to 0.54 and in wall thickening from 33% to 15%. Subendocardial flow fell 48%. Coronary blood flow and thickening were constant during 1 hour of ischemia. Phosphocreatine (mumol/g wet wt) in the subendocardial third of the ischemic zone fell from 7.6 to 3.8 at 5 minutes of ischemia (p less than 0.005 versus control) and returned to normal (7.9) at 60 minutes (p = NS), despite ongoing ischemia. Subendocardial ATP (mumol/g wet wt) fell slowly from 4.3 and leveled off at 2.1 at 60 minutes of ischemia (p less than 0.001 versus control). Similar regeneration of phosphocreatine was found in seven additional pigs, with a 43% transmural reduction in coronary blood flow and a 66% reduction in subendocardial flow. No significant changes in ATP and phosphocreatine were noted in two different control groups (n = 13 pigs). The regeneration of phosphocreatine despite ongoing ischemia and low ATP levels was not related to changes in myocardial oxygen demand or consumption, or in regional function during the period of ischemia. This may reflect 1) a successful downregulation of the energy needs of the ischemic myocardium to maintain cell viability, or 2) a metabolic abnormality in the ability of the cells to produce ATP primarily or by use of phosphocreatine.

Topics: Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Hemodynamics; Myocardium; Oxygen Consumption; Phosphocreatine; Regeneration; Swine; Time Factors

This study compares the metabolism and functional responses of adult and immature hearts to a standard ischemic insult. Ten adult dogs (25 to 27 kg) and 10 puppies (6 to 10 weeks old) underwent 45 minutes of aortic clamping on bypass. Preoperative and postoperative ventricular performance (Starling curves), biochemical factors, and water content were measured. Global ischemia in adults produced a 30% mortality rate (3/10) and low output syndrome in survivors (33% recovery of stroke work index). Conversely, all puppies survived and stroke work index returned to 85% of control, with less edema developing (0.4% versus 2% water gain, p less than 0.05). Puppies expended comparable glycogen stores but used more glutamate (15.4 versus 8.6 mumol/gm dry weight), produced more alanine (18.9 versus 6.4 mumol, p less than 0.05), succinate (19 versus 8.2 mumol, p less than 0.05), and malate (2.6 versus 0.15 mumol, p less than 0.05) during ischemia, and recovered better postischemic aerobic metabolism (410 versus 255 nmol tissue pyruvate, p less than 0.05). We conclude that tolerance of immature hearts to ischemia is related to amino acid utilization by transamination and increased substrate level phosphorylation, as occurring in diving mammals, suggesting retention of intrautero adaptive mechanisms.

Topics: Adenosine Triphosphate; Aging; Amino Acids; Animals; Aorta; Body Water; Citric Acid Cycle; Constriction; Coronary Circulation; Coronary Disease; Dogs; Glycogen; Heart; Myocardium; Phosphocreatine; Ventricular Fibrillation; Ventricular Function, Left

This study tests the importance of amino acid transamination in determining the tolerance of immature hearts to ischemic damage. Amino acid transamination was inhibited metabolically by pretreatment with aminooxyacetic acid. The aminooxyacetic acid dose and duration were determined by incubating in vitro tissue homogenate and showing that an 8 mmol/L AOA dose for 5 minutes blocked 90% of alanine aminotransferase and aspartate aminotransferase activity. Control studies in nonischemic hearts showed that coronary perfusion with aminooxyacetic acid for 5 minutes did not impair myocardial performance. In contrast, pretreatment of immature puppies with aminooxyacetic acid severely impaired recovery after 45 minutes of normothermic global ischemia (30% versus 85% recovery in untreated hearts, p less than 0.05). Biochemical analyses of hearts undergoing ischemia showed aminooxyacetic acid to limit lactate production, impair glutamate utilization, prevent alanine production, and limit succinate accumulation (p less than 0.05). These data suggest that amino acid transamination is an important adaptive process in the immature heart that improves its resistance to ischemic damage.

Topics: Adenosine Triphosphate; Aging; Amino Acids; Aminooxyacetic Acid; Animals; Aorta; Body Water; Constriction; Coronary Circulation; Coronary Disease; Dogs; Glycogen; Heart; Lactates; Lactic Acid; Myocardium; Phosphocreatine; Ventricular Function, Left

Effects of low-flow perfusion after zero-flow ischemia on myocardial mechanical function and energy metabolism were studied with 31P nuclear magnetic resonance spectroscopy, using isolated perfused rat hearts. After control perfusion, hearts were randomly divided into five experimental groups: Groups I and II were subjected to zero-flow ischemia of 40 and 60 min, respectively. In groups III-V the perfusion was resumed at a rate of 0.1 ml/min after 40 (group III), 30 (group IV) and 20 (group V)-min of zero-flow ischemia in order to compare the effects of low-flow perfusion with those of persistent zero-flow. After these interventions all the hearts were perfused for 40 min at a normal flow rate. Compared with the hearts exposed to total ischemia of 60 min, the preservation of high energy phosphate compounds (HEP) was better in groups with early low-flow perfusion; Creatine phosphate (CrP) levels, which had decreased rapidly after induction of zero-flow ischemia, increased gradually after initiation of the low-flow perfusion and reached significantly higher levels at the end of ischemic period in groups IV and V than in group II (p less than 0.05). The decrease in adenosine triphosphate (ATP) was likewise significantly suppressed by low-flow perfusion (groups IV and V greater than group II). Restoration of CrP levels after complete reperfusion was also significantly greater in group V than in group II. The recovery of ATP after complete reperfusion was also much better in group V being comparable to those in group I, although the total duration of ischemia was longer in group V than in group I. These results indicate the beneficial effects of low-flow perfusion on the preservation during ischemia and recovery after reperfusion of myocardial HEP.

Topics: Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Energy Metabolism; Heart; Hydrogen-Ion Concentration; In Vitro Techniques; Magnetic Resonance Spectroscopy; Male; Myocardium; Perfusion; Phosphates; Phosphocreatine; Rats; Rats, Inbred Strains

This study analyzes the importance of the source and rate of ATP production (glucose flux, glycogenolysis, and oxidative phosphorylation) in the prevention of ischemic contracture in isolated rat hearts. Ischemic contracture was initiated at about 10 minutes by buffer perfusion with nonglycolytic substrates whereas the addition of 11 mM glucose prevented contracture for 2 hours. Tissue values of ATP, phosphocreatine, and lactate could be dissociated from onset of ischemic contracture. In hearts perfused with acetate or free fatty acid, with 11 mM glucose, glycolytic ATP production was 2.3-2.8 mumol/g fresh wt/min; as initial rates of glycogenolysis fell, glycolysis was maintained by a steady increase of glucose flux to values in excess of 2 mumol ATP/g fresh wt/min. Decreasing the glucose flux by lowering the perfusate glucose or by the addition of 2-deoxyglucose precipitated ischemic contracture. When oxidative phosphorylation was further reduced by hypoxia, glucose still prevented ischemic contracture; however, when oxidative phosphorylation dropped to near zero (near-anoxic) rates, glycolysis was inhibited, and glucose could only delay ischemic contracture to about 45 minutes. Combined ATP production rates could be dissociated from contracture. The metabolic parameter that correlated best with prevention or delay of ischemic contracture was the rate of glycolytic flux from glucose, which in this model of global low-flow ischemia had to accelerate to provide a rate of ATP production from glucose in excess of 2 mumol/g fresh wt/min within 30 minutes of the start of ischemia to prevent ischemic contracture.

Topics: Acetates; Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Fatty Acids, Nonesterified; Glucose; Glycogen; Heart; Lactates; Lactic Acid; Male; Myocardial Contraction; Phosphocreatine; Rats; Rats, Inbred Strains; Time Factors

We explored the effects of sustained low-flow ischemia on function and metabolism in isolated neonatal hearts. The hearts were extracted from 21 piglets (1-12 days old) and set up as modified Langendorff preparations beating isometrically. They were perfused with red blood cell-enhanced buffer at controlled rates of coronary flow. Mechanical measurements, O2 usage, and substrate oxidation were determined simultaneously at 30-minute intervals for 2 hours. In control hearts, coronary flow was maintained at 1.8 ml/min/g. There was no significant change in mechanical function, diastolic compliance, or O2 or substrate metabolism after 2 hours. In the ischemia group, coronary flow was reduced to 0.2 ml/min/g and sustained for 2 hours. With the onset of ischemia, mechanical function promptly fell to 20% of control. Although O2 delivery was reduced to 11%, O2 extraction doubled so that myocardial O2 consumption was 22% of control, matching mechanical function. Glucose oxidation fell from 37 to 12 nmol/min/g, and lactate release appeared. These measures and ventricular compliance remained constant for the full 2 hours. Concentrations of glycogen and creatine phosphate did not differ from the control group; ATP was 76% of controls. These studies indicate that when myocardial O2 supply is limited, mechanical function rapidly diminishes, largely preserving critical energy stores and preventing irreversible myocellular injury. Although the signal remains to be determined, the strategy is similar to that employed by hibernating species to survive extended periods of O2 deprivation.

Topics: Adenosine Triphosphate; Animals; Animals, Newborn; Biological Availability; Coronary Circulation; Coronary Disease; Diastole; Glycogen; Heart; Hibernation; In Vitro Techniques; Myocardium; Oxidation-Reduction; Oxygen; Oxygen Consumption; Perfusion; Phosphocreatine; Swine

Relationships between myocardial Ca2+ uptake, recovery of ventricular function, and restoration of tissue metabolites were determined during 30 min of reperfusion following ischemic and anoxic perfusion with either zero or low coronary flow, zero flow with intermittent perfusion, and low-flow perfusion without substrates. When zero-flow ischemia was maintained for 30 or 40 min, tissue lactate levels increased approximately 100-fold; with reperfusion of these hearts, developed pressure recovered to only 70 and 40% of preischemic function, respectively, and Ca2+ uptake increased by 7- and 15-fold. In contrast, 30 min of low-flow (1 ml/min) anoxic perfusion resulted in accumulation of less lactate (15-fold increase), less reperfusion Ca2+ uptake, and recovery of developed pressure to the preanoxic level. Omission of energy substrates during the low-flow anoxic perfusion caused a reduced recovery of heart rate with lower high-energy phosphate levels and increased Ca2+ uptake, but contractile function recovered to the same extent as in low-flow perfusion with substrate. Even very low flow rates (0.06-0.16 ml/min) of oxygen-deficient perfusate increased high-energy phosphate content and contractile function and decreased Ca2+ uptake. Intermittent perfusion with either oxygenated or anoxic buffer between four 10-min episodes of ischemia reduced lactate accumulation, maintained function, and left Ca2+ uptake essentially unchanged. Recovery of developed pressure during reperfusion was negatively correlated with the amount of lactate that accumulated during ischemia or anoxia and with reperfusion Ca2+ uptake, regardless of the duration or type of ischemia or anoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Calcium; Coronary Circulation; Coronary Disease; Coronary Vessels; Diastole; Hypoxia; In Vitro Techniques; Male; Myocardial Reperfusion; Myocardium; Perfusion; Phosphocreatine; Rats; Rats, Inbred Strains; Regional Blood Flow; Time Factors

The mechanisms responsible for changes in myocardial contractility during regional ischemia are unknown. Since changes in high-energy phosphates during ischemia are sensitive to reductions in myocardial blood flow, it was hypothesized that myocardial function under steady-state conditions of graded regional ischemia is closely related to changes in myocardial high-energy phosphates. Therefore, phosphorus-31 nuclear magnetic resonance spectroscopy was employed in an in vivo porcine model of graded coronary stenosis. Simultaneous measurements of regional subendocardial blood flow, high-energy phosphates, pH, and myocardial segment shortening were made during various degrees of regional ischemia in which subendocardial blood flow was reduced by 16-94%. During mild reductions in myocardial blood flow (subendocardial blood flow = 83% of nonischemic myocardium), only the ratio of phosphocreatine to inorganic phosphate (PCr/Pi), Pi, and [H+] were significantly changed from control. PCr, ATP, and PCr/ATP were not significantly reduced from control with mild reductions in blood flow. Changes in myocardial segment shortening were most closely associated with changes in PCr/Pi (r = 0.94). Pi and [H+] were negatively correlated with segment shortening (r = -0.64 and -0.58, respectively) and increased over twofold when blood flow was reduced by 62%. Thus, these data demonstrate that PCr/Pi is sensitive to reductions in myocardial blood flow and closely correlates with changes in myocardial function. These data are also consistent with a role for Pi or H+ as inhibitors of myocardial contractility during ischemia.

Topics: Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Energy Metabolism; Female; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Myocardial Contraction; Myocardium; Phosphocreatine; Swine

Delayed recovery of contractile function after myocardial ischemia may be due to prolonged recovery of high-energy phosphates, persistent acidosis, increased inorganic phosphate, and/or calcium loading. To examine these potential mechanisms, metabolic parameters measured by 31P nuclear magnetic resonance spectroscopy, and spontaneous diastolic myofilament motion caused by sarcoplasmic reticulum-myofilament calcium cycling indexed by the scattered light intensity fluctuations (SLIF) it produces in laser beam reflected from the heart, were studied in isolated atrioventricularly blocked rat hearts (n = 10) after 65 min of ischemia at 30 degrees C. All metabolic parameters recovered to their full extent 5 min after reperfusion. Developed pressure evidenced a small recovery but then fell abruptly. This was accompanied by an increase in end diastolic pressure to 37 +/- 5 mm Hg and a fourfold increase in SLIF, to 252 +/- 58% of baseline. In another series of hearts initial reperfusion with calcium of 0.08 mM prevented the SLIF rise and resulted in improved developed pressure (74 +/- 3% vs. 39 +/- 13% of control), and lower cell calcium (5.9 +/- 3 vs. 10.3 +/- 1.4 mumol/g dry wt). Thus, during reperfusion, delayed contractile recovery is not associated with delayed recovery of pH, inorganic phosphate, or high-energy phosphates and can be attributed, in part, to an adverse effect of calcium loading which can be indexed by increased SLIF occurring at that time.

Topics: Adenosine Triphosphate; Animals; Calcium; Coronary Disease; Diastole; Magnetic Resonance Spectroscopy; Male; Myocardial Contraction; Myocardial Reperfusion; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains

The time course of the relative myocardial phosphocreatine and adenosine triphosphate contents (PCr/ATP) during step changes in heart rate in vivo was studied in 14 dogs using 31P nuclear magnetic resonance (NMR) to determine if transient changes in the high energy phosphates occur with changes in cardiac work. Coronary sinus blood flow (CF), oxygen consumption (MVO2), and NMR data were simultaneously measured during brief (approximately 3 min), paced increases in heart rate in these open chest animals. 31P spectra were collected with a time resolution of 15-16 s (PCr signal to noise 22-41:1). Paced tachycardia associated with increased CF and MVO2 had no significant transient or sustained effect on PCr/ATP. Higher heart rates, associated with decreased CF and blood pressure, caused rapid decreases of PCr/ATP that were reversible upon return to control rates. These data indicate that there are no transient changes in 31P metabolites (on a 15-16-s time base) during step changes in cardiac work associated with increased CF. This lack of change demonstrates that ATP hydrolysis and production are closely matched and that the feedback mechanism linking these processes occurs rapidly with no detectable transient change in the phosphate metabolites. In contrast, when the CF response to tachycardia is insufficient PCr is quickly depleted. This latter result suggests that the PCr/ATP ratio may be a sensitive, rapidly responding indicator of coronary supply/demand mismatching in vivo.

Topics: Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Dogs; Female; Hemodynamics; Magnetic Resonance Spectroscopy; Male; Myocardium; Oxygen Consumption; Phosphocreatine

The effect of pH of the reperfusion buffer on postischemic changes in tissue Ca and Na was examined in isolated Langendorff-perfused Sprague-Dawley rat hearts. Reperfusion began after 15-, 25-, or 60-min ischemia at 37 degrees C. After 60-min ischemia, reperfusion at pH 6.4 or 6.6 attenuated the reperfusion-induced Ca gain so long as the acidotic conditions were maintained (3.08 +/- 0.22, 1.37 +/- 0.41, and 16.96 +/- 1.18 mumol Ca gain/g dry wt for pH 6.4, 6.6, and 7.4, respectively after 15-min reperfusion). Conversely, reperfusion under alkalotic conditions (pH 7.9) after 60-min ischemia exacerbated the gain (27.45 +/- 4.75 and 8.92 +/- 1.53 mumol Ca gain/g dry wt during 5-min reperfusion at pH 7.9 and 7.4, respectively). Similar, but less pronounced Ca gains occurred during reperfusion after 15- or 25-min ischemia. Sodium content during reperfusion, but not during aerobic perfusion, was also found to be pH sensitive with acidosis causing a reduction and alkalosis an increase. These results could not be explained in terms of an effect of pH on recovery of high-energy phosphates, percentage "reflow" during reperfusion, or reperfusion-induced increases in tissue water or resting tension. The results are in agreement with the hypothesis that the "inhibitory" effect of acidosis on postischemic Ca overload could involve an effect of pH on the Na(+)-H+ exchanger and intracellular Ca storage.

Topics: Acidosis; Acidosis, Respiratory; Adenosine Triphosphate; Alkalosis; Alkalosis, Respiratory; Animals; Biomechanical Phenomena; Buffers; Coronary Disease; Female; Hydrogen-Ion Concentration; In Vitro Techniques; Mitochondria, Heart; Myocardial Reperfusion; Perfusion; Phosphocreatine; Rats; Rats, Inbred Strains; Time Factors

Angina is characterized by brief periods of ischemia followed by reperfusion; the cumulative effect of these episodes on energetics of the myocardium has not been fully elucidated. This study used an in vivo feline model for the assessment of high-energy phosphate compounds during brief sequential periods of ischemia and reperfusion. Nine adult, open-chest, anesthetized cats were prepared with a reversible occluder around the proximal left anterior descending artery and a 1.2-cm-inside diameter coil sutured on the myocardial surface in the distribution of the left anterior descending coronary artery. Levels of PCr, Pi, and ATP (beta-phosphate signal) were measured by 31P MRS in a GE CSI 2-T NMR spectrometer/imager. Measurements were obtained during a control period and during three successive occlusion-deocclusion periods of roughly 12 and 20 min' duration, respectively. The last deocclusion period was observed for 60 min. Electron microscopy was performed in two animals. PCr declined (P less than 0.01) rapidly following each occlusion to 51 +/- 5.2% (occlusion 1), 53 +/- 5.8% (occlusion 2), and 48 +/- 5.7% (occlusion 3) of the control value by 6 min. Pi rose (P less than 0.01) with the three sequential occlusions to 253 +/- 46, 288 +/- 57, and 277 +/- 46%, respectively. PCr and Pi returned to baseline promptly with reperfusion, while ATP showed a gradual decline throughout the experiment, decreasing to 77 +/- 7.2% of control at the end of the last reperfusion (P less than 0.05). Although PCr returned to baseline during reperfusion, ATP did not, suggesting a reduction in the nucleotide pool. These findings indicate that the repeated episodes of ischemia, which are insufficient to produce necrosis, can have an effect on myocardial high-energy phosphate metabolism as evidenced by mild depletion of ATP.

Topics: Adenosine Triphosphate; Animals; Cats; Coronary Disease; Magnetic Resonance Spectroscopy; Myocardium; Phosphates; Phosphocreatine

The effects of dichloroacetate (DCA), which is known to have a beneficial effect on lactic acidosis, were examined on myocardial acidosis during coronary occlusion in dogs. Ischemia was induced by complete ligation of the left anterior descending coronary artery (LAD) of the open-chest dog heart. DCA 100 mg/kg or 200 mg/kg was administered intravenously 10 or 60 min prior to the occlusion of LAD. DCA did not change the LAD flow, decreased heart rate, increased both systolic and diastolic blood pressures transiently. LAD occlusion significantly increased the ST segment of the epicardial ECG in the saline-treated group. DCA administered prior to the LAD occlusion caused 50% decrease of the elevation in ST segment during ischemia. Ischemia accelerated anaerobic metabolism in the myocardium; the levels of glycogen, adenosine triphosphate (ATP) and creatine phosphate (CP) decreased, and lactate increased during ischemia. Calculated energy charge potential was decreased, and [( G6P] + [F6P])/[FDP] ratio was increased by ischemia. The decreased levels of glycogen, ATP, CP in DCA-treated group were similar to those in saline-treated group during 3 min ischemia. Pretreatment of DCA reduced the accumulation of myocardial lactate by ischemia. There were no differences in variables except myocardial lactate levels between DCA 100 mg/kg and 200 mg/kg. The myocardial lactate levels were lower in both nonischemic and ischemic dogs by DCA 200 mg/kg than DCA 100 mg/kg. DCA did not change either the ATP levels or energy charge potential during both ischemia and reperfusion. LAD occlusion caused a significant decrease of myocardial pH from 7.51 to 6.83 in saline-treated group, while it produced only a small decrease in DCA-treated group from 7.56 to 7.35.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Acetates; Adenine Nucleotides; Animals; Coronary Disease; Dichloroacetic Acid; Dogs; Energy Metabolism; Glycolysis; Hemodynamics; Hydrogen-Ion Concentration; Myocardium; Phosphocreatine

The aim of the study was to assess the contribution of adenine nucleotide depletion to postischaemic myocardial dysfunction ("stunned" myocardium).. Isolated perfused hearts release purine catabolites even in the absence of ischaemia, and undergo spontaneous reduction of adenine nucleotide pool. A comparison was therefore made between mechanical function, purine release and tissue adenine nucleotides in working rat hearts reperfused after short term ischaemia or subjected to prolonged perfusion (up to 180 min).. 49 Sprague-Dawley rats of 250-300 g body weight were used. The animals were anaesthetised and the hearts quickly excised and perfused with the working heart technique.. Reperfusion after 10 min ischaemia provided a good model of "stunned" myocardium: aortic flow and minute work decreased by 15(SEM 2)% and 20(3)%, no enzyme leakage was observed, and the adenine nucleotide pool decreased by 3.5(0.4) mumols.g-1. During prolonged perfusion no change was observed in any haemodynamic variable until the adenine nucleotide pool was depleted by over 8.5 mumols.g-1. Adenylate energy charge and the phosphocreatine-creatine pool were unchanged in all cases.. Depletion of adenine nucleotides does not account for contractile dysfunction in our model of "stunned" myocardium.

Topics: Adenine Nucleotides; Animals; Coronary Disease; Creatine; In Vitro Techniques; Myocardial Contraction; Myocardial Reperfusion; Myocardium; Phosphocreatine; Purines; Rats; Rats, Inbred Strains; Regional Blood Flow

1. In isolated rat heart ventricular myocytes exposed to 2 mM-cyanide in the presence of 10 mM-2-deoxyglucose (complete metabolic blockade), there is a time-dependent increase in ATP-sensitive potassium (KATP) channel activity. The increase in KATP channel activity accompanies the decline of twitch amplitude. Channel activation and decline of the twitch amplitude precede the development of a 'rigor' contracture. 2. We measured KATP channel activity in permeabilized cells using the open-cell attached (O-C-A) patch configuration (by establishing a cell-attached patch and then permeabilizing the cell by exposure to saponin). The apparent ATP dependence of KATP channel activity could be described by a sigmoid curve with ki, ATP (ATP concentration required for half-maximum inhibition of channel activity) = 122 microM and H (Hill coefficient) = 1.225. 3. In the O-C-A patch configuration, 10 mM-creatine phosphate (CrP) decreased the apparent ki, ATP from 122 microM to about 10 microM, and the maximal activity (in zero ATP) was decreased to about 30% of the maximal activity in the absence of CrP. 4. In isolated inside-out (I-O) patches, ATP inhibited KATP channel activity at much lower [ATP] than in the O-C-A patch configuration (ki, ATP = 25 microM, H = 2). CrP was without effect on I-O patches. 5. These results are consistent with the hypothesis that the difference in the ATP dependence of KATP channel activity in the O-C-A and I-O patch configurations arises because of ATP consumption in the O-C-A patch configuration. The results suggest that hydrolysis of ATP to ADP by endogenous ATPases leads to the development of gradients of [ATP] and [ADP] between the bath and the 'inside' of the open cell. By re-phosphorylating ADP, CrP is able to dissipate these gradients, revealing the 'true' ATP dependence of channel activity, which is the same as that in the I-O patch configuration. 6. In order to estimate the contribution of KATP channel activity to the rat cardiac action potential at different [ATP] we have made the following measurements. Using electrodes of resistance 2-8 M omega the density of KATP channels was 10.3 +/- 0.1 channels per patch (n = 162).(ABSTRACT TRUNCATED AT 400 WORDS)

Topics: Action Potentials; Adenosine Triphosphate; Animals; Antimetabolites; Coronary Disease; Electrophysiology; In Vitro Techniques; Myocardium; Permeability; Phosphocreatine; Potassium Channels; Rats

Spatially localized nuclear magnetic resonance spectroscopy was used to investigate with transmural differentiation the response of myocardial high energy phosphate compounds and inorganic orthophosphate (Pi) to graded reductions in coronary blood flow caused by sustained coronary stenosis. In an open-chest model, localized 31P nuclear magnetic resonance spectra from five layers across the left ventricular wall were obtained simultaneously with transmural blood flow measurements during control conditions and during sustained graded reductions in intracoronary pressure. Both the blood flow, and high energy phosphate and Pi contents displayed transmural heterogeneity in response to decreases in intracoronary pressure. The subendocardial creatine phosphate (CP) level remained unchanged as blood flow was reduced to approximately 0.7 ml/min/g wet wt and decreased precipitously beyond this critical flow level. The relation between CP and flow in the midmyocardium and especially in the subepicardium was more complex. Subepicardial CP content did not correlate well with blood flow; however, in cases in which a coronary stenosis resulted in subendocardial hypoperfusion but subepicardial flow was near or above normal, a close correlation was present between subepicardial and subendocardial CP levels. ATP levels in all layers remained unaltered until blood flow was severely reduced. These results demonstrate that 1) the myocardial high energy phosphate and Pi levels at any transmural layer are not generally determined by O2 and blood flow limitation under basal conditions; 2) during subtotal coronary occlusion, increased oxygen extraction is able to meet myocardial needs until a critical level of stenosis is reached; 3) below a critical flow level, subendocardial CP and Pi contents are closely correlated with absolute subendocardial blood flow; and 4) in the presence of a coronary stenosis, subepicardial CP and Pi contents may change even in the absence of perfusion deficit secondary to loss of subendocardial function.

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Constriction, Pathologic; Coronary Circulation; Coronary Disease; Dogs; Magnetic Resonance Spectroscopy; Myocardium; Oxidative Phosphorylation; Phosphates; Phosphocreatine

The effect of high concentration of magnesium on both mechanical dysfunction and metabolic damage after ischaemia-reperfusion was studied in isolated rat hearts. The heart was perfused by the Langendorff's technique at a constant flow (10 ml/min) with modified Krebs-Henseleit solution and driven at 300 beats/min. The heart was made ischaemic by reducing the flow to 0 ml/min for 25 min, and then reperfused at the constant flow for 15 min. MgSO4 was added to the perfusate for 5 min before the onset of ischaemia, or after the end of ischaemia (after the onset of reperfusion). Ischaemia-reperfusion produced both mechanical dysfunction (as evidenced by an increase in the left ventricular end diastolic pressure and a decrease in the left ventricular developed pressure) and metabolic damage [as evidenced by a decrease in the myocardial adenosine triphosphate (ATP)]. When 15 mmol/l MgSO4 was given before ischaemia, there was no appreciable recovery of mechanical function, whereas when given after ischaemia (during reperfusion), there was a marked recovery of mechanical function. Lower concentrations (10 or 5 mmol/l) of MgSO4 given after ischaemia recovered the mechanical function concentration-dependently. The beneficial effect of 15 mmol/l MgSO4 was minimized by the coexistence of 4.5 mmol/l CaCl2 in the reperfusion solution. The decrease in the myocardial level of ATP induced by ischaemia-reperfusion was attenuated by 15 mmol/l MgSO4 given in the reperfusion solution. These results suggest that high Mg2+ is effective in attenuating both functional and metabolic damage of the post-ischaemic heart, provided it is given after ischaemia.

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Coronary Disease; Energy Metabolism; Heart; Heart Function Tests; In Vitro Techniques; Magnesium; Male; Myocardial Reperfusion; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains

We hypothesized that the antiarrhythmic efficacy of propranolol during acute myocardial ischemia could be dose related. Propranolol was administered in two equally divided doses 30 min before and 10 min after ligation of the anterior descending coronary artery (CAL) in anesthetized open-chest pigs. Only the lowest dose of propranolol, i.e., 0.1 mg/kg intravenously (i.v.) (plasma level 22 +/- 2 ng/ml) decreased the incidence of ventricular fibrillation (VF), i.e. 3 of 12 versus 16 of 20 in control group (p less than 0.01). VF incidence with propranolol 0.5 or 3 mg/kg was 4 of 6 and 8 of 9, respectively (both NS vs. control group). Propranolol 0.1 mg/kg did not change left ventricular (LV) blood flow. Propranolol 3 mg/kg reduced blood flow in the peripheral ischemic myocardium to 13.2 +/- 1.2 versus 19.2 +/- 1.4 ml/100 g/min in control group (p less than 0.01), and in the midischemic zone to 4.4 +/- 0.5 versus 7.0 +/- 0.9 ml/100 g/min in control group (p less than 0.001). Propranolol 0.1 mg/kg prevented a disparity of levels of cyclic AMP from arising between ischemic and non-ischemic myocardium, whereas propranolol 3.0 mg/kg did not. Furthermore, LV mechanical function was suppressed by propranolol 3 mg/kg. Only the lowest dose of propranolol (i.e., 0.1 mg/kg) decreased the incidence of VF in this model.

Topics: Adenosine Triphosphate; Adrenergic beta-Antagonists; Animals; Coronary Circulation; Coronary Disease; Cyclic AMP; Female; Male; Myocardium; Phosphocreatine; Propranolol; Swine; Ventricular Fibrillation

The effects of equipotent doses in negative inotropic and chronotropic properties of nipradilol [10 micrograms/kg/min intravenously (i.v.)] and propranolol (20 micrograms/kg/min i.v.) on hemodynamics and transmural energy metabolites in ischemic hearts were examined in anesthetized dogs. After 5-min infusion of these agents, coronary perfusion pressure of 30 mm Hg was induced by acute coronary stenosis for 10 min. Coronary blood inflow and myocardial contractile force (MCF) in the control ischemic area decreased to about one-third and two-thirds of the respective starting levels. In the nipradilol group, similar changes were observed, but in the propranolol group the MCF tended to decrease further. Cardiac effort index decreased to about two-thirds in both groups. The left ventricular end-diastolic pressure (LVEDP) increased by 4.3 mm Hg with saline, by 8.8 mm Hg with propranolol, and by 1.3 mm Hg with nipradilol. ATP depletion in the ischemic myocardium (by 29 and 22% in inner and outer layers, respectively) was restored to normal level by either agent. A decrease in creatine phosphate and an accumulation of lactate were significantly alleviated by nipradilol (by 74 and 59----by 39 and 21%, and by 4.9 and 2.3----by 0.7 and 0.2 times, respectively), but not by propranolol. The results indicate that in addition to a decrease in myocardial oxygen consumption caused by the beta-adrenoceptor blocking effects of nipradilol, reductions in preload and afterload caused by the vasodilating property significantly contribute to nipradilol-induced improvement in the ischemic derangement of transmural energy metabolism.

Topics: Animals; Blood Pressure; Cardiac Output; Coronary Disease; Coronary Vessels; Dogs; Energy Metabolism; Heart; Heart Rate; Lactates; Male; Myocardium; Phosphates; Phosphocreatine; Propanolamines; Propranolol; Vasodilator Agents

The influence of PGE1, iloprost and a combination of both on high energy phosphate levels in isolated rat hearts reperfused 1 h following 20 min of global ischemia was investigated employing 31P-NMR-spectroscopy. Whereas PGE1 induced a slight reduction in the decline of the creatine phosphate/inorganic phosphate. ATP/inorganic phosphate ratio and NMR-energetic index during ischemia, iloprost application was followed predominantly by a temporary but marked improvement of the creatine phosphate/inorganic phosphate ratio during the early period of reperfusion. The best results in preservation of high energy phosphates were achieved after simultaneous application of PGE1 and iloprost. It is presumed that the accelerated normalization of the heart function observed immediately after ischemia in the eicosanoid treated hearts is related to the more rapid recovery of intracardial high energy phosphate level.

Topics: Adenosine Triphosphate; Alprostadil; Animals; Cardiovascular Agents; Coronary Disease; Epoprostenol; Heart; Iloprost; Kinetics; Magnetic Resonance Spectroscopy; Male; Myocardial Reperfusion; Myocardium; Phosphates; Phosphocreatine; Phosphorus; Rats; Rats, Inbred Strains; Reference Values

To assess whether pretreatment with the calcium antagonist anipamil protects the heart against ischemic and reperfusion damage and to establish how long the protection persists after cessation of the therapy, rabbits were injected subcutaneously twice daily for 5 days with 2 mg/kg body weight of this drug. The heart was then isolated 2, 6, or 12 hours after the last injection and was perfused by the Langendorff technique during a control period and 90 minutes of total ischemia (37 degrees C), followed by 30 minutes of reperfusion. Diastolic and developed pressure was monitored; coronary effluent was collected and assayed for creatine phosphokinase (CPK); mitochondria were harvested and assayed for respiratory activity, ATP production, and calcium content; and tissue concentration of adenosine triphosphate (ATP) and creatine phosphate were determined. The data obtained with anipamil were compared with those obtained with verapamil administered to the rabbit at the same dose and following the same procedure. Pretreatment with anipamil induced a negative inotropic effect under normoxic conditions; reduced the rate and extent of depletion of ATP and creatine phosphate during ischemia, with an incomplete restoration of the nucleotides after reperfusion; maintained mitochondrial function and calcium homeostasis during ischemia and reperfusion; reduced the rate of CPK release; and improved the recovery of ventricular function on reperfusion. The protective effects of anipamil persisted for as long as 12 hours after the last administration. In contrast, the protective and negative inotropic effects of verapamil were no longer apparent in heart isolated 6 or 12 hours after the last dose of the drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Calcium Channel Blockers; Coronary Disease; Creatine Kinase; In Vitro Techniques; Mitochondria, Heart; Myocardial Reperfusion; Myocardium; Oxygen Consumption; Phosphocreatine; Propylamines; Proteins; Rabbits; Verapamil

The ability to resist transient ischemia was studied in isolated hearts of 18 months old spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats. Both types of hearts showed optimal performance during the preischemic period when perfused at a diastolic perfusion pressure of 8.0 (WKY) and 13.3 (SHR) kPa. Hemodynamic recovery of WKY hearts during reperfusion at 8.0 kPa, following 45 min global ischemia, was satisfactory. coronary perfusion completely normalized, contractility (dPlv/dtmax) was slightly depressed and cardiac output returned, on the average, to 40% of the preischemic values. In contrast, hemodynamic function of SHR hearts reperfused at 13.3 kPa was greatly depressed, as evidenced by almost complete abolition of cardiac output, severe reduction of dPlv/dtmax and persistent underperfusion of the endocardial layers. In addition, the postischemic release of lactate dehydrogenase was retarded and enhanced. The release patterns of degradation products of adenine nucleotides showed a shift to the endstage products xanthine and uric acid. The enhanced vulnerability of the hypertrophied heart to ischemia was even more expressed when the SHR hearts were reperfused at 8.0 kPa. Postischemic function was characterized by electrical instability, loss of contractility and cardiac output, and noreflow in the endocardial layers. Persistent accumulation of lactate and degradation products of adenine nucleotides in the postischemic hearts are in line with the lack of reperfusion. The present results indicate that a detailed mechanistic explanation for the reduced ability to withstand ischemia of SHR cannot be based on differences in ATP content or an altered anaerobic glycolitic activity prior and during ischemia. It is suggested that a defect on the circulatory level, probably caused by enhanced reactivity of the coronary vessels towards ischemia-elicited factors, is responsible for the higher vulnerability of hypertrophied heart to an ischemia insult.

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Cardiac Output; Cardiomegaly; Coronary Circulation; Coronary Disease; Glycogen; L-Lactate Dehydrogenase; Myocardial Contraction; Myocardial Reperfusion; Phosphates; Phosphocreatine; Rats; Rats, Inbred SHR; Rats, Inbred WKY

We examined the effect of nicorandil and nipradilol on the ischemic myocardium in the isolated perfused rat heart. The heart was perfused by the working heart technique with an afterload pressure of 60 mm Hg and with a left atrial filling pressure of 9 mm Hg. Ischemia was induced for 20 min by lowering the afterload pressure. The afterload pressure was raised to 60 mm Hg again during reperfusion. Ischemia decreased the pressure-rate product, coronary flow, adenosine triphosphate level and creatine phosphate level, and increased the lactate level. Reperfusion could not restore the pressure-rate product nor the adenosine triphosphate level completely. Nicorandil (5 x 10(-5) and 1.5 x 10(-4) M) or nipradilol (10(-5), 5 x 10(-5) and 1.5 x 10(-4) M) was introduced 5 min before ischemia. Nipradilol preserved the levels of adenosine triphosphate and creatine phosphate after 20 min of ischemia and increased the extent of recovery of the pressure-rate product during reperfusion, whereas nicorandil did not. Nipradilol, but not nicorandil, can protect the myocardium against ischemic damage.

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Coronary Circulation; Coronary Disease; Heart; In Vitro Techniques; Lactates; Male; Niacinamide; Nicorandil; Phosphocreatine; Propanolamines; Rats; Rats, Inbred Strains

The effects of palmitate on mechanical failure of ischemic hearts were studied in acutely (48-hour) and chronically (6-week) streptozotocin diabetic rats. Coronary flow was reduced by 50% in isolated working hearts perfused at a 15 cm H2O preload and 100 mm Hg afterload by the one-way ball valve model of ischemia. Peak systolic pressure (PSP) and cardiac output (CO) decreased 40% by 4 minutes in control hearts perfused with 11 mM glucose and paced at 280 beats/min, compared with 50% in hearts from acutely diabetic rats. Addition of 1.2 mM palmitate to the perfusate accelerated failure rates, with PSP and CO decreasing 65% and 80% by 4 minutes in control and acutely diabetic rat hearts, respectively. In chronically diabetic rats, mechanical function could not be maintained in palmitate-perfused hearts paced at 280 beats/min, even in the absence of ischemia. If these hearts were paced at 250 beats/min and subjected to ischemia, PSP and CO decreased 90% by 4 minutes, regardless of whether palmitate was added to the perfusate. Under these conditions, PSP decreased less than 10% by 4 minutes in both palmitate- or glucose-perfused control hearts. Etomoxir (10(-9) M), a carnitine palmitoyltransferase I inhibitor, markedly decreased the rate of mechanical failure in both acutely and chronically diabetic rat hearts, in the presence and absence of palmitate. The beneficial effect of Etomoxir on mechanical function did not occur as a result of a decrease in either myocardial long chain acyl-coenzyme A or long chain acylcarnitine levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Acute Disease; Acyl Coenzyme A; Acyltransferases; Animals; Carnitine O-Palmitoyltransferase; Chronic Disease; Coronary Disease; Diabetes Mellitus, Experimental; Epoxy Compounds; Fatty Acids; Heart; In Vitro Techniques; Male; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains; Streptozocin; Thiourea

Amlodipine is a long-acting dihydropyridine-based Ca2+ channel blocker, developed for use on a once-daily basis. Experiments using hearts from amlodipine-pretreated rats were undertaken to further test the hypothesis that Ca2+ channel blockers can be used as prophylactic therapy to reduce the severity of the mechanical and biochemical consequences of ischemia and reperfusion. Amlodipine was given intravenously, 0.25 mg/kg, 5 hours before excising the hearts. Ischemia (global) was induced at 37 degrees C for 10, 30 or 60 minutes, and was followed by reperfusion. Protection was quantitated in terms of functional recovery, adenosine triphosphate and creatine phosphate retention, tissue acidosis and Ca2+ gain. The results show that amlodipine pretreatment supplied protection, provided that the ischemic episode did not exceed 30 minutes. The protection resulted in improved recovery of peak developed tension on reperfusion, reduced Ca2+ gain, retention of tissue adenosine triphosphate and creatine phosphate, and reduced acidosis.

Topics: Acidosis; Adenosine Triphosphate; Amlodipine; Animals; Calcium; Calcium Channel Blockers; Coronary Disease; Heart Rate; In Vitro Techniques; Male; Myocardial Contraction; Myocardial Reperfusion Injury; Myocardium; Nifedipine; Phosphocreatine; Rats; Rats, Inbred Strains; Reperfusion; Time Factors

The effects of the dihydropyridine calcium-channel blocker, amlodipine, on subendocardial segment shortening (%SS), regional myocardial blood flow, myocardial high-energy phosphate levels and tissue water content were compared to those of a saline-treated group of barbital-anesthetized dogs subjected to a 45-minute coronary artery occlusion followed by 60 minutes of reperfusion. Saline or amlodipine (200 micrograms/kg, IV) were administered 15 minutes prior to coronary occlusion. There were no significant differences between groups in ischemic bed size or hemodynamics, although dP/dt was higher following amlodipine. Subepicardial collateral blood flow was higher in the amlodipine group during coronary occlusion. Following occlusion, %SS in the ischemic region was markedly decreased in both series and passive systolic lengthening resulted. In spite of similar decreases in %SS during occlusion, the amlodipine- treated dogs showed a marked improvement in myocardial segment function (%SS) of the ischemic-reperfused region throughout 60 minutes of reperfusion as compared to saline-treated animals. In addition, amlodipine prevented the rebound increase in phosphocreatine and attenuated the loss of adenine nucleotides and the increase in tissue water in the ischemic-reperfused area at 60 minutes of reperfusion. These results suggest that amlodipine has a favorable effect on the functional and metabolic recovery of the ischemic-reperfused myocardium, and may have potential as a therapeutic agent for the treatment of coronary artery disease. The mechanism of action of amlodipine in this model is unknown but may be partially related to a drug-induced increase in coronary collateral blood flow.

Topics: Adenine Nucleotides; Amlodipine; Animals; Calcium Channel Blockers; Coronary Disease; Coronary Vessels; Dogs; Female; Heart; Hemodynamics; Male; Myocardial Reperfusion Injury; Myocardium; Nifedipine; Phosphates; Phosphocreatine; Water

The effect of low flow ischemia and subsequent reperfusion with 5.5 mM glucose or 5 mM acetate on energy metabolism and catabolism of myocardial glutamate and aspartate was studied in isolated perfused guinea pig hearts. Reperfusion with acetate was followed by low recovery of the cardiac contractile function associated with a great rise in isovolumic end-diastolic pressure. It was combined with more profound losses of tissue adenine nucleotides and the total Cr compared to reperfusion with glucose. The total glutamate and aspartate pool decreased more than two-fold compared to the initial one regardless of substrate. However, glutamate content was reduced by 58 and 38% with acetate and glucose, respectively. The expenditure of both amino acids was caused by alanine formation stimulated by glycolysis/glycogenolysis. The remaining glutamate and aspartate pool in the reperfused hearts positively correlated with adenine nucleotides (r = 0.62), the total creatine (r = 0.65), and the recovery of contractile function (r = 0.64). The results suggest that the glutamate and aspartate pool may be of critical importance for postischemic functional and metabolic recovery of the heart.

Topics: Adenosine Triphosphate; Animals; Aspartic Acid; Coronary Disease; Creatine; Energy Metabolism; Glutamates; Glutamic Acid; Guinea Pigs; Histocytochemistry; Lactates; Lactic Acid; Male; Myocardial Contraction; Myocardium; Phosphocreatine

Diltiazem may provide a protective effect to ischemic and reperfused myocardium through preservation of high-energy phosphate metabolism. To test this hypothesis, rabbits had a 1.3 cm solenoidal coil placed over the myocardium to be rendered ischemic. Data were acquired with a 22 cm bore nuclear magnetic resonance spectrometer at 2.0 T. Animals were treated with diltiazem (200 micrograms/kg intravenous bolus of drug followed by a 15 micrograms/kg/min continuous intravenous infusion, n = 10) or by an equal volume of saline (n = 6). The left circumflex artery was occluded and reperfused using a reversible snare while electrocardiogram-gated spectra were accumulated. Levels of phosphocreatine were decreased during occlusion in both groups; however, this decrease was attenuated in the diltiazem treated animals compared to control (in relative percent area: 7.8 +/- 1.0 to 2.5 +/- 0.5, p less than 0.01). Levels of phosphocreatine promptly returned to baseline following reperfusion and there was no difference between the two groups. The inorganic phosphate metabolites of high-energy phosphate consumption increased with occlusion, though more so in the control group compared with the diltiazem-treated rabbits (in relative percent area: 72.5 +/- 0.9 to 55.4 +/- 1.3, p less than 0.01). With reperfusion, levels of inorganic phosphates returned toward baseline in both groups; however, the diltiazem group had a more complete recovery relative to control (in relative percent area: 38.8 +/- 2.1 to 47.6 +/- 2.7, p less than 0.05). Levels of adenosine triphosphate decreased in both groups relative to baseline; however, the amount of decrease was similar in the two groups. With reperfusion there was a definite though incomplete recovery of levels of adenosine triphosphate in the diltiazem-treated group (in relative percent area: 10.7 +/- 1.0 at occlusion, 12.3 +/- 0.4 during reperfusion, p less than 0.05), but in the control group levels of adenosine triphosphate remained depressed (in relative percent area: 9.8 +/- 0.6 at occlusion, 9.8 +/- 0.8 during reperfusion, p = NS). During ischemia there was a trend toward attenuation of intracellular acidosis in the diltiazem group; however, this trend did not reach statistical significance. These data indicate that diltiazem provides a protective effect on myocardial high-energy phosphate metabolism during regional ischemia and reperfusion in the intact animal.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Diltiazem; Magnetic Resonance Spectroscopy; Myocardial Reperfusion; Phosphates; Phosphocreatine; Phosphorus; Rabbits

The Langendorff perfused rat heart was used to investigate whether myocardial damage during ischemia and reperfusion could be protected by free radical scavengers, calcium antagonist and adenosine. Myocardial high energy phosphates were measured by phosphorus-31 NMR spectroscopy during normal perfusion, 20 min of ischemia and 20 min of reperfusion. In hearts, which were treated both with free radical scavengers (FRS) (Superoxide dismutase): 24 IU/ml and catalase 22 IU/ml) and verapamil (10(-7) M), beta-ATP was significantly higher than that of FRS at the end of ischemia. However, beta-ATP recovered only to 83% of baseline value at the end of reperfusion. In view of myocardial metabolism, verapamil treated hearts were good for recovery of creatine phosphate (PCr) but not ATP at the end of reperfusion. Hearts which were treated with only adenosine did not differ from control hearts. However, when hearts were treated with both verapamil and adenosine (10(-4) M), recovery of both ATP and PCr content was significantly greater than that of control hearts. These results suggested that pretreatment with both verapamil and adenosine before and after global ischemia could protect ischemic myocardium, but, further studies are necessary to clarify the precise mechanism of protection.

Topics: Adenosine; Adenosine Triphosphate; Animals; Catalase; Coronary Disease; Heart; In Vitro Techniques; Magnetic Resonance Spectroscopy; Male; Myocardial Reperfusion Injury; Myocardium; Phosphocreatine; Phosphorus; Rats; Rats, Inbred WKY; Superoxide Dismutase; Verapamil

Magnesium (Mg2+) is an important regulator of cell energy metabolism, since only MgATP can serve as a substrate for ATP utilizing processes. We used 31P NMR spectroscopy to determine the complexation of ATP with Mg2+ and intracellular free Mg2+ (Mgf) in isolated rat hearts during control perfusion, ischemia and reperfusion. Atomic absorption spectrophotometry was used to determine preischemic and postischemic tissue Mg2+ and release of Mg2+ into the coronary effluent during reperfusion. Mgf increased from 0.60 mmol/l during control perfusion to greater than 6.5 mmol/l after 15 min of ischemia, while we estimated that at that time 6.7 mmol/l Mg2+ had been liberated from ATP. Less than 2% of cellular Mg2+ was released to the effluent during reperfusion after 30 min of ischemia. From spectra obtained during reperfusion the fraction of ATP that was bound to Mg2+ was calculated to be approximately 96% (compared to 94% during control perfusion), indicating that intracellular Mg2+ did not limit the metabolic use of the newly produced ATP. Mgf remained elevated during reperfusion (0.85 mmol/l). We conclude that intracellular Mg2+ deficiency due to leakage of Mg2+ to the extracellular space does not play a role in the poor postischemic recovery in this isolated rat heart model. Nevertheless, high Mg2+ prior to ischemia or during reperfusion may well be protective, due to interactions of Mg2+ with the sarcolemma or intracellular sites, affecting Ca2+,K+ and Na+ distribution and fluxes.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Energy Metabolism; Intracellular Fluid; Magnesium; Magnetic Resonance Spectroscopy; Male; Myocardial Reperfusion; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains

To establish if the administration of gallopamil, a derivative of verapamil, protects heart muscle against the deleterious effect of ischemia and subsequent reperfusion, rabbits were injected subcutaneously twice daily with 2 mg/kg of Gallopamil for 5-6 days. The hearts were isolated and perfused with aerobic Krebs-Henseleit buffer solution by the Langendorff method. The hearts were paced (180 b/min) and wall temperature was controlled. Ischemia was induced by reducing coronary flow from 25 ml/min to 1 ml/min for 90 min and then the hearts were reperfused for 30 min. At the end of either the ischemic period or reperfusion, the hearts were assayed for ATP, CP, and calcium. Others were homogenized, their mitochondria harvested and monitored for oxidative phosphorylating and ATP generating activity as well as calcium content and uptake. The mechanical function of the hearts and noradrenaline release was also measured. Hearts that were made ischemic gained calcium, their endogenous stores of ATP and CP were depleted, their mitochondria had reduced RCI and state 3 respiration and increased calcium concentrations. During reperfusion tissue and mitochondrial calcium was significantly increased, the capacity of mitochondria to use oxygen for state 3 respiration was further impaired and their ATP generating capacity reduced. Diastolic pressure increased and there was no recovery of developed pressure and important noradrenaline release. Pretreatment with gallopamil protected the mitochondria against the ischemically induced changes in RCI, state 3 respiration. There was also a less marked rise in tissue and mitochondrial calcium and a reduced increase of diastolic pressure. Gallopamil also diminished the effect of reperfusion on the calcium accumulating activity of mitochondria and on the decline in the ATP generating and oxygen utilizing capacity of the mitochondria. The tissue levels of ATP and CP were better maintained, and noradrenaline release was reduced, the systolic pressure generating capacity was enhanced by the treatment with gallopamil. These results are discussed in accordance with the hypothesis that this drug protects heart muscle against the deleterious effects of ischemia and reperfusion by ensuring that sufficient ATP remains available to maintain homeostasis with respect to calcium.

Topics: Adenosine Triphosphate; Animals; Calcium; Coronary Disease; Gallopamil; Male; Mitochondria, Heart; Myocardial Contraction; Myocardial Reperfusion Injury; Myocardium; Norepinephrine; Oxygen Consumption; Phosphocreatine; Rabbits

To investigate the cause for the greater susceptibility of hypertrophied hearts to ischemic injury, we determined the interrelations of total work output, contractile function and energy metabolism in isolated, perfused normal and hypertrophied rat hearts subjected to graded global ischemia. Cardiac hypertrophy was induced by giving rats seven daily injections of either triiodothyronine (0.2 mg/kg) or isoproterenol (5 mg/kg). All hearts were perfused at an aortic pressure of 100 mmHg in the isovolumic mode in an NMR spectrometer (7.05 Tesla). Heart rate, developed pressure, and coronary flow were monitored simultaneously with changes in pH, creatine phosphate, ATP and inorganic phosphate. During pre-ischemic perfusion, the total work output (rate-pressure product) of hyperthyroid hearts was 28% higher than that of control hearts, whereas hearts from isoproterenol-treated animals showed no difference. However, when related to unit muscle mass, work was normal in hyperthyroid hearts and 26% lower after isoproterenol. Contractile function per unit myocardium (developed pressure/g wet weight) was lower in the hypertrophied hearts. ATP content was the same in all groups. Creatine phosphate decreased 41% after triiodothyronine and 25% after isoproterenol. Inorganic phosphate levels and intracellular pH were similar in control and isoproterenol-treated rat hearts, but were higher in the hyperthyroid rat hearts. The phosphorylation potential and the free energy change of ATP hydrolysis were lowered by hypertrophy, the levels correlating with the depressed contractile function. At each ischemic flow rate, both work and contractile function per unit myocardium were the same for all hearts, but the relations between flow and phosphorylation potential were different for each type of heart. Thus, at low flow rates, hypertrophied hearts perform the same amount of work and have the same contractile function as control hearts, but with abnormal changes in energy metabolism, indicating that the relations of energy status to coronary flow, total work output and contractile function are altered during the process of hypertrophy.

Topics: Adenosine Triphosphate; Animals; Cardiomyopathy, Hypertrophic; Chromatography, High Pressure Liquid; Coronary Disease; Cytosol; Isoproterenol; Magnetic Resonance Spectroscopy; Male; Myocardial Contraction; Myocardium; Phosphocreatine; Phosphorylation; Rats; Rats, Inbred Strains; Triiodothyronine

The changes in myocardial high energy phosphates and pH during regional ischemia, and their potential role in mediating functional abnormalities, is unclear. To determine the degree of regional blood flow reduction required to induce changes in high energy phosphates and pH, and to correlate these metabolic changes with alterations in blood flow, 31P nuclear magnetic resonance spectroscopy was employed in an in vivo porcine model of graded coronary stenosis. Simultaneous measurements of regional blood flow and phosphate compounds were made during various steady-state degrees of regional ischemia in which subendocardial blood flow was reduced by as much as 80%. ATP did not fall over the total range of graded ischemia, while phosphocreatine (PCr), inorganic phosphate (Pi), and pH all changed progressively after blood flow was reduced below 50% of normal. The ratio of PCr/Pi (a measure of the energy reserve of the myocardium) was strongly correlated to subendocardial blood flow (r = 0.94) and declined by 25% when blood flow was reduced by only 21% below normal. These findings indicate that PCr/Pi is a sensitive marker of ischemia and support the hypothesis that the in vivo energy status of the myocardium is closely coupled to myocardial blood flow.

Topics: Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Female; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Myocardium; Phosphates; Phosphocreatine; Phosphorylation; Swine

The influence of exogenous creatine phosphate (CP) on peroxidative heart injury was investigated in two experimental models: isolated working rat hearts and myocardial membrane preparations. In the first model the addition of 190 microM hydrogen peroxide to the perfusion buffer caused a marked decrease of aortic flow, minute work and peak aortic pressure, and leakage of intracellular enzymes. In the presence of 10 mM CP the hemodynamic damage produced by the same concentration of hydrogen peroxide was significantly lower and enzyme release was also remarkably reduced. The protection was concentration-dependent and the whole structure of the molecule was required since creatine was found to be ineffective. In the absence of hydrogen peroxide, CP and creatine did not affect heart performance. In microsomal membrane preparations CP decreased the formation of thiobarbituric acid-reactive material (malonaldehyde) induced by hydrogen peroxide in the presence of ferrous ions. This protection was concentration-dependent and occurred at physiological concentrations of CP. Also in this experimental model creatine had no effect and creatine plus inorganic phosphate was much less active than CP. The influence of CP on oxidative heart stress could account for the beneficial effect of this substance in different models of ischemic injury.

Topics: Animals; Coronary Disease; Creatine; Heart; Hemodynamics; Hydrogen Peroxide; Hypoxia; In Vitro Techniques; Lipid Peroxidation; Male; Membrane Lipids; Phosphocreatine; Rats; Rats, Inbred Strains; Stress, Physiological

Seventy-eight dogs with graded constriction of the left main coronary artery were studied to determine the coronary blood flow at which the heart is vulnerable to catecholamine induced ischemia. The left main coronary artery was cannulated with a Griggs' type self-perfusing cannula. The coronary blood flow (CBF) was reduced by graded constriction of the extra-corporeal circuit connected with this cannula. Blood flow rates between 12 and 117 ml/min/100 g were studied. Cardiac activation was achieved by either intracoronary administration of a physiological dose of catecholamine (noradrenaline; 0.4 microgram/kg/min or adrenaline; 0.2 microgram/kg/min), or by electrical stimulation of the left stellate ganglion (4 Hz, 2 msec, 10 V for 5 min). When CBF was below 30 ml/min/100 g, accentuated myocardial ischemia was always indicated by lactate production, myocardial creatine phosphate depletion, ischemic ST segment changes, and elevated left ventricular end diastolic pressure (LVEDP) during these stimulations. When CBF was above 50 ml/min/100 g, catecholamine clearly accelerated the cardiac function and myocardial metabolism with no signs of ischemia. When CBF was between 30 and 50 ml/min/100 g signs of accentuated myocardial ischemia appeared during catecholamine activation in only 1/2 of the dogs. This study indicated that the critical level for CBF at which endogenous or exogenous catecholamine can produce ischemia is between 30 and 50 ml/min/100 g.

Topics: Adrenergic Fibers; Animals; Blood Pressure; Coronary Circulation; Coronary Disease; Dogs; Electric Stimulation; Electrocardiography; Epinephrine; Female; Heart; Lactates; Male; Myocardium; Norepinephrine; Oxygen Consumption; Phosphocreatine; Stellate Ganglion

This study was designed to define the effect of postischemic low Ca2+ perfusion on recovery of high-energy phosphates, intracellular pH, and contractile function in isolated rat hearts. Phosphorus-31 nuclear magnetic resonance spectroscopy was used to follow creatine phosphate, adenosine triphosphate, intracellular inorganic phosphate, and intracellular pH during control perfusion (15 minutes), total ischemia (30 minutes), and reperfusion (30 minutes). In Group I the perfusate [Ca2+] was 1.3 mmol/l throughout the experiment, whereas in Group II the perfusate [Ca2+] was reduced to 0.05 mmol/l during the first 10 minutes of reperfusion. Hearts from Group III were not made ischemic but were subjected to 10 minutes of low Ca2+ perfusion followed by 20 minutes of normal Ca2+ perfusion. During low Ca2+ reperfusion (Group II) recovery of high-energy phosphates and pH was significantly better than in controls (Group I). However, after reexposure to normal Ca2+, metabolic recovery was largely abolished, coronary flow was suddenly impaired, and contracture developed without any rhythmic contractions. These observations indicated the occurrence of a calcium paradox rather than postponed ischemia-reperfusion damage. On the other hand, normoxic hearts (Group III) tolerated temporary perfusion with 0.05 mmol/l Ca2+ very well with respect to left ventricular developed pressure, coronary flow, and metabolic parameters. In conclusion, postischemic low Ca2+ (0.05 mmol/l) perfusion may reduce reperfusion damage, but at the same time ischemia appears to enhance the susceptibility of the heart to the calcium paradox.

Topics: Adenosine Triphosphate; Animals; Calcium; Coronary Circulation; Coronary Disease; Hydrogen-Ion Concentration; In Vitro Techniques; Magnetic Resonance Spectroscopy; Male; Myocardial Contraction; Myocardial Reperfusion; Myocardial Reperfusion Injury; Myocardium; Phosphates; Phosphocreatine; Rats; Rats, Inbred Strains

Ischemic dysfunction, including contracture, has been attributed to lack of ATP, although previous work has not been consistent with this concept. We describe here a model of no flow ischemic arrest, characterized by depressed levels of mechanical function upon reperfusion and high energy phosphate stores within normal limits. The decreased mechanical function bears an inverse relationship to myocardial lactate levels after twenty-minutes of reperfusion in the absence or presence of dichloroacetic acid (DCA). Post-ischemic non-DCA treated hearts attained peak work of only 25% of that of controls, while those treated with DCA following ischemia performed almost as well as controls. ATP and CP levels remained high in both DCA treated and non-DCA treated hearts. Lactate levels were high in hearts immediately following ischemia, but were reduced to control levels in post-ischemic hearts perfused with DCA within twenty minutes, whereas those not treated with DCA had lactate levels two to three times that of controls within the same time period. Pyruvate dehydrogenase (PDH) activity was reduced in non-DCA treated post ischemic hearts after twenty minutes reperfusion but was elevated above controls in hearts reperfused with DCA. The data indicates that DCA increases mechanical performance of the isolated post-ischemic rat heart and the proposed mechanism for this increase is the oxidative removal of lactate resulting from an increase in PDH activity.

Topics: Acetates; Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Dichloroacetic Acid; In Vitro Techniques; Lactates; Male; Myocardial Contraction; Myocardium; Phosphocreatine; Pyruvate Dehydrogenase Complex; Rats

The effect of flunarizine, a calcium entry-blocker, on the ischemic myocardial metabolism of the open-chest dog heart was examined and compared to that of diltiazem. During ischemia, initiated by ligating the left anterior descending coronary artery, the metabolism of the myocardium switched from aerobic to anaerobic; the levels of glycogen, fructose-1,6-diphosphate (FDP), adenosinetriphosphate and creatinephosphate decreased, and the levels of glucose-6-phosphate (G6P), fructose-6-phosphate (F6P), lactate, adenosine diphosphate and adenosine monophosphate increased during 3 min of ischemia. The calculated energy charge potential decreased, and the [( G6P] + [F6P]/[FDP] ratio and the lactate/pyruvate ratio were increased by ischemia. Flunarizine (0.3 or 1 mg/kg) or diltiazem (0.1 mg/kg) was injected i.v. 5 min before the start of ischemia. Pretreatment with either flunarizine or diltiazem reduced the decrease in the energy charge potential and the increase in the [( G6P] + [F6P]/[FDP] ratio during ischemia. Flunarizine (1 mg/kg) and diltiazem (0.1 mg/kg) reduced the accumulation of lactate due to ischemia, leading to a decrease in the lactate/pyruvate ratio. Flunarizine and diltiazem may lessen the influence of ischemia on the myocardial tissue.

Topics: Adenine Nucleotides; Animals; Blood Pressure; Coronary Circulation; Coronary Disease; Diltiazem; Dogs; Female; Flunarizine; Fructose; Glucose; Glucosephosphates; Glycogen; Heart Rate; Male; Myocardium; Phosphocreatine

In an attempt to define the metabolic abnormalities of the ischemic myocardium, the changes in high energy phosphates, inorganic phosphate and intracellular pH were serially and quantitatively evaluated in ischemic porcine hearts having no collateral circulation, using arterial pressure and respiration gated in vivo 31P magnetic resonance spectroscopy. The protocol was also modified for propranolol pretreatment (0.6 mg/kg intravenously) to define its effect on the metabolism of ischemic myocardium. In the non-treated group, creatine phosphate was rapidly depleted by 10 minutes after ischemia; by 40 minutes, ATP and intracellular pH gradually decreased to 10 +/- 11% of control and to 5.90 +/- 0.26, respectively, and inorganic phosphate rose to 303 +/- 43% of control. In the propranolol treated group, the concentrations of creatine phosphate and ATP were higher, and those of inorganic phosphate and tissue pH were similar compared with controls during 40 minutes of ischemia. This suggests that the beneficial effect of propranolol on the ischemic myocardium is due to the preservation of ATP, an essential energy resource for numerous enzymatic reactions in viable myocardium.

Topics: Acid-Base Equilibrium; Adenosine Triphosphate; Animals; Blood Pressure; Coronary Disease; Energy Metabolism; Heart Rate; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Myocardium; Phosphates; Phosphocreatine; Propranolol; Respiration; Swine

Phosphorus NMR spectroscopy is an important technique for the investigation of metabolism in tissues and intact organisms (including man). However, quantitation of the signals from an NMR experiment is difficult because it is not known from which regions of a cell metabolites are detected. It is generally believed that only metabolites free in the cytosol are observed. In this study a comparison of concentration measurements obtained by NMR and after freeze extraction was made in the normoxic and ischemic rat heart. The influence of ischemia was examined because of its potential effect on the level of phosphate metabolites in various compartments. The same fraction of ATP always appears visible to NMR, whereas inorganic phosphate is largely NMR invisible until after a period of ischemia and the phosphomonoesters are only partially observed early in ischemia.

Topics: Adenosine Monophosphate; Animals; Coronary Disease; Energy Metabolism; Glucose-6-Phosphate; Glucosephosphates; Glycerophosphates; In Vitro Techniques; Magnetic Resonance Spectroscopy; Male; Myocardium; Perfusion; Phosphates; Phosphocreatine; Phosphorus; Phosphorylation; Rats; Rats, Inbred Strains

Recovery of contractile function of myocardium stunned by a brief, transient period of regional ischemia is highly variable. In our experience, segment shortening (an index of regional systolic contractile function) assessed during the initial hours after a 15-minute period of coronary artery occlusion in anesthetized open-chest dogs ranged from -84 to +99% of normal preocclusion values. In this retrospective study, regression analysis was used to assess the effects of various parameters on segment shortening 2 hours after reperfusion. Parameters assessed included regional myocardial blood flow both during occlusion and after reperfusion, high-energy phosphate content of previously ischemic tissue, systemic hemodynamic parameters (heart rate, mean arterial pressure and double product), occluded bed size and segment shortening measured during coronary artery occlusion. Recovery of systolic contractile function was not influenced by the degree of ischemia during coronary artery occlusion, myocardial blood flow after reperfusion, high-energy phosphate content, hemodynamic parameters or occluded bed size (correlation coefficients, r, ranged from 0.001 to 0.37 [p = not significant]). Only the degree of dyskinesia/hypokinesia exhibited during coronary occlusion significantly and reliably predicted recovery of segment shortening measured 2 hours after reflow (r = 0.70, p less than 0.001). Thus, recovery of systolic contractile function in the anesthetized canine model of the stunned myocardium is determined primarily by the degree of dysfunction exhibited during the preceding period of ischemia.

Topics: Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Dogs; Hemodynamics; Myocardial Contraction; Myocardium; Phosphocreatine; Retrospective Studies

The cardioprotective effects of nifedipine, verapamil, diltiazem, bepridil, CERM 11956, lidoflazine, mioflazine and the coronary vasodilator dipyridamole were evaluated in the guinea-pig working heart with respect to cardiac function and high energy phosphate content after 45 min of global ischaemia and 25 min of reperfusion. All drugs, with the exception of dipyridamole, induced a negative inotropic effect, which resulted in a decrease of the aortic pressure (AoP), of its first derivative dAoP/dt and the cardiac output. To compare the anti-ischaemic effect of the calcium antagonists, concentrations were selected that reduced the dAoP/dt by 10% (EC10) and 30% (EC30), respectively. With the exception of nifedipine at the EC10 and bepridil and CERM 11956 at the EC30, perfusion with the calcium antagonists and dipyridamole (3 mumol/l) improved the recovery of contractile function after global ischaemia and reperfusion to a value between 60 and 80% of the controls in normoxic hearts. Pretreatment with nifedipine, verapamil, diltiazem, lidoflazine and mioflazine, but not with bepridil, CERM 11956 and dipyridamole led to slightly increased ATP levels in ischaemic hearts as compared to the control value in ischaemic hearts. After subsequent reperfusion for 25 min, for all drugs, ATP levels were further enhanced to 50% of the level in normoxic hearts; phosphocreatine levels reached normoxic values. In particular at the EC30, the effects of calcium antagonists on cardiac function varied in accordance with their known pharmacological and physiological profile. However, there appeared to exist no direct relationship between their beneficial effects on contractile activity and those on the levels of high energy phosphates after ischaemia and reperfusion.

Topics: Adenine Nucleotides; Animals; Blood Pressure; Calcium Channel Blockers; Cardiac Output; Coronary Circulation; Coronary Disease; Dipyridamole; Guinea Pigs; Heart; Heart Diseases; In Vitro Techniques; Male; Myocardial Contraction; Myocardial Reperfusion Injury; Myocardium; Phosphocreatine

Previous studies have demonstrated that both myocardial metabolism and ventricular function were depressed after blood cardioplegic arrest for elective coronary artery bypass grafting. To evaluate the etiology of this metabolic defect, we measured the levels of adenine nucleotides and their precursors in 29 patients undergoing elective coronary revascularization. Myocardial biopsy specimens were obtained at 37 degrees C before cardioplegic arrest, immediately after 74 +/- 4 minutes of cardioplegic arrest, and after 30 minutes of reperfusion. Biopsy specimens were analyzed for levels of adenine nucleotides and their precursors by high-performance liquid chromatography. Adenosine triphosphate concentrations decreased with cardioplegic arrest and with reperfusion. Adenosine monophosphate concentrations increased after cardioplegic arrest and remained nearly twice the initial values after reperfusion. The ratio of adenosine monophosphate to adenosine triphosphate doubled after reperfusion, suggesting defective conversion of adenosine monophosphate to adenosine triphosphate. Levels of adenine nucleotide degradation products (adenosine, inosine, and hypoxanthine) increased after cardioplegia and decreased with reperfusion, suggesting a washout of soluble precursors. This study suggests that improvements in myocardial protection should attempt to stimulate mitochondrial energy production and preserve adenine nucleotide precursors.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Blood; Body Temperature; Chromatography, High Pressure Liquid; Coronary Artery Bypass; Coronary Disease; Heart Arrest, Induced; Humans; Hypoxanthine; Hypoxanthines; Middle Aged; Myocardium; Phosphocreatine; Time Factors; Uric Acid

The effect of lidocaine on the accumulation of non-esterified fatty acids (NEFA) was investigated in the isolated, perfused working rat heart. Ischemia was induced by lowering the afterload pressure to 0 mm Hg for 20 min, and reperfusion was induced by raising the pressure to the pre-ischemic value (60 mm Hg) for 20 min. The heart was frozen for biochemical studies immediately after ischemia or reperfusion. Ischemia decreased the mechanical function, increased the levels of palmitoleic, arachidonic and linoleic acids, left unchanged the levels of oleic, lauric, myristic, palmitic and stearic acids, decreased the levels of adenosine triphosphate (ATP), creatine phosphate (CrP), decreased the energy charge potential (ECP) and increased the level of lactate. Lidocaine (10(-5) or 3 x 10(-5) M) improved the mechanical function and attenuated the changes in NEFA, ATP, CrP, and ECP caused by ischemia. These findings suggest that lidocaine attenuates the ischemia- and reperfusion-induced metabolic changes in the myocardium.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Energy Metabolism; Fatty Acids, Nonesterified; Heart; In Vitro Techniques; Lactates; Lidocaine; Male; Myocardial Reperfusion; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains

The effects of ischemia and cardiac arrest by cardioplegia on the mechanical function and energy metabolism of the ventricular myocardium of the neonatal guinea pig were investigated in the isolated perfused heart preparation and compared with these effects in the adult guinea pig. Whereas reperfusion after ischemia resulted in better recovery of mechanical function and a higher adenosine triphosphase content in the neonatal myocardium than in the adult, recovery from cardiac arrest induced by St. Thomas' Hospital cardioplegic solution was not as good in the neonatal myocardium as in the adult. Contracture developed in the neonatal myocardium on administration of the cardioplegic solution, but did not in the adult. This was considered to be the reason that the protective effect of the cardioplegic solution was inferior in the neonatal myocardium to that in the adult.

Topics: Adenosine Triphosphate; Animals; Animals, Newborn; Blood Pressure; Coronary Circulation; Coronary Disease; Guinea Pigs; Heart; Heart Arrest, Induced; Humans; In Vitro Techniques; Lactates; Myocardial Reperfusion; Phosphocreatine

Few studies have examined metabolic consequences of coronary occlusion and reperfusion using phosphorus31 nuclear magnetic resonance (31P-NMR) in an intact animal model. Accordingly, we developed a model to study serial changes in myocardial metabolism in the intact open-chest rabbit. Ten animals underwent 20 +/- 2 minutes of regional coronary occlusion and 60 +/- 10 minutes of reperfusion followed by reocclusion. Cardiac-gated 31P-NMR spectra were obtained with a regional surface coil over the ischemic area during baseline, occlusion, reperfusion, and reocclusion conditions. Phosphocreatine fell with both the initial and second ischemic insults to 65% +/- 5% of baseline for the first occlusion (p less than 0.01) and tended to decrease to 89% +/- 8% of baseline for the second occlusion (p = 0.07), with normal levels reattained in the intervening period of reperfusion (99% +/- 5% of baseline, p = NS). Concordant inverse changes were seen with inorganic phosphates. At occlusion levels of inorganic phosphates were 135% +/- 10% of baseline (p less than 0.05) and 139% +/- 10% of baseline at reocclusion (p less than 0.05). Levels of adenosine triphosphate decreased during occlusion to 78% +/- 9% of baseline and were significantly lower than baseline during the second occlusion (75% +/- 5% of baseline, p less than 0.01). The ratio of phosphocreatine to inorganic phosphates, when compared with values at baseline, decreased at occlusion (49.6% +/- 4.7% of baseline, p less than 0.01) and at reocclusion (64.7% +/- 4.9% of baseline, p less than 0.01), with a normal ratio reattained in the intervening period of reperfusion (93.3% +/- 3.1% of baseline, p = NS). We conclude that reperfusion restores levels of phosphocreatine and adenosine triphosphate while returning levels of inorganic phosphates to baseline. Deleterious changes in high-energy phosphate metabolism are not potentiated by reocclusion in this model. 31P-NMR spectroscopy holds promise as a technique to noninvasively monitor intracellular biochemical processes serially during various interventions in the intact animal model.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Magnetic Resonance Spectroscopy; Myocardial Reperfusion; Myocardium; Phosphates; Phosphocreatine; Rabbits

Isolated rat heart perfusion and high-resolution phosphate-31 nuclear magnetic resonance (31P-NMR) spectroscopy were used to elucidate the effects of Mg during reperfusion of the ischemic myocardium. After an ischemic period of 9 min, the hearts were reperfused with 0, 0.6, or 2.4 mM Mg during the entire 24-min reperfusion period or with 15 mM Mg during the first 12 min before returning to the physiological concentration of 0.6 mM during the last 12 min. Free intracellular Mg calculated by 31P-NMR rose during ischemia and fell gradually during reperfusion. The two groups reperfused with 15 mM Mg exhibited a significantly enhanced rate of recovery of adenosine triphosphate, creatine phosphate, intracellular pH, and coronary flow rate than the three other groups. Myocardial potassium was significantly higher, and inorganic phosphate was significantly lower at the end of the reperfusion period in these groups. The hearts reperfused with 0 mM Mg presented a significantly higher frequency of ventricular fibrillation (VF) than the other groups. It is concluded that reperfusion with high Mg improves the postischemic recovery of metabolism and function in the rat heart, whereas a Mg-free reperfusion solution increases the frequency of VF.

Topics: Adenosine Triphosphate; Animals; Chromatography, High Pressure Liquid; Coronary Circulation; Coronary Disease; Heart Rate; Hydrogen-Ion Concentration; Magnesium; Magnetic Resonance Spectroscopy; Male; Myocardial Reperfusion; Phosphocreatine; Rats; Rats, Inbred Strains

We tested the hypothesis that inhibition of adenosine transport by dipyridamole and inhibition of adenosine deamination by erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA) prevents nucleoside loss and stimulates postischemic ATP-repletion. In an open chest canine model, dipyridamole (0.5 mg/kg/h) and EHNA (5 mg/kg/h) were infused intra-atrially during a coronary occlusion period of 45 min and a reperfusion period of 180 min. Transmural needle biopsies, obtained during the ischemic period and within the reperfusion period, were analyzed using high performance liquid chromatography for adenine nucleotides and adenosine, inosine, xanthine, and hypoxanthine as well as creatine phosphate. During ischemia and under the influence of dipyridamole plus EHNA, 56% of the catabolized adenine nucleotides were recovered stoichiometrically as adenosine, whereas in the untreated group less than 10% of the nucleotides were recovered as adenosine because of rapid deamination to inosine. In the control group, ATP levels decreased during ischemia from control values of 5.25 +/- 0.28 microns/g to 2.01 +/- 0.18 microns/g. In the group treated with dipyridamole and EHNA, ATP levels fell to 2.2 +/- 0.22 microns/g but rose to 3.22 +/- 0.29 microns/g within 180 min of reperfusion, whereas in the untreated control group tissue levels of ATP did not increase. However, a significant proportion of the adenosine accumulated during ischemia under the influence of dipyridamole plus EHNA was not used for the restoration of the ATP level during reperfusion. A significant amount of adenosine was probably trapped in the interstitial space and could not be transported back into the myocytes in the presence of dipyridamole during reperfusion. In both groups, creatine phosphate levels were restored to normal levels during reperfusion.

Topics: Adenine Nucleotides; Adenosine Triphosphate; Animals; Coronary Disease; Dogs; Female; Hemodynamics; In Vitro Techniques; Male; Myocardium; Nucleosides; Phosphocreatine

Topics: Adenosine Triphosphate; Calcium; Coronary Disease; Glycolysis; Humans; Myocardium; Perfusion; Phosphocreatine; Phospholipids; Superoxides

To determine the buffering capacity of ischemic rat myocardium, lactate production was altered by glycogen depletion prior to total global ischemia. Lactate production was monitored by 1H-NMR spectroscopy in perfused rat hearts and determined by enzymatic assay of freeze-clamped tissue extracts. Intracellular pH was measured by 31P-NMR spectroscopy. The relationship between total lactate produced and pH varied considerably, depending on the final pH reached. At pH greater than 6.4 this relationship is linear with a total buffering capacity (delta lactate/delta pH) of 25 mumol H+/g wet weight per pH unit. At lower pH values (pH less than 6.4), the total buffering capacity increases progressively. Since ischemia is invariably accompanied by ATP and phosphocreatine (PCr) hydrolysis, the proton production/consumption during high-energy phosphate hydrolysis must be considered when evaluating the intrinsic buffering capacity of the myocardium against proton loads produced by lactate production from glucose and glycogen. Schemes are presented which allow an estimation of the contribution of ATP and PCr hydrolysis and the buffering by the CO2/HCO3- system during ischemia. At pH greater than 6.4, the majority (about 60%) of buffering is due to hydrolysis of adenosine triphosphate, phosphocreatine in the heart, and neutralization of sodium bicarbonate in the perfusate. At pH less than 6.4 an increasing proportion of cardiac buffering is from intrinsic cardiac buffers, most likely from intracellular proteins. After correction for these contributions to the observed total cardiac buffering capacity, the intrinsic buffering capacity of the myocardium can be accounted for by a high capacity (170 mumol/g wet weight) but low pKa (5.2) buffering system.

Topics: Adenosine Triphosphate; Animals; Bicarbonates; Buffers; Coronary Disease; Hydrogen-Ion Concentration; Hydrolysis; Lactates; Magnetic Resonance Spectroscopy; Male; Myocardium; Perfusion; Phosphates; Phosphocreatine; Protons; Rats; Rats, Inbred Strains

The effects of exogenous glutamate (20 mM) on myocardial energy metabolism and cardiac function during low-flow ischaemia and subsequent reperfusion were studied in isolated working rat hearts. Hearts were made severely ischaemic for 60 min by reducing the perfusion rate to 0.17 ml/min, and then reperfused for 30 min. Low-flow ischaemia resulted in a 50% reduction of myocardial ATP, a 70% reduction of both creatine phosphate (CP) and GTP, and a 250% rise in AMP. After reperfusion, CP was restored to normal levels but ATP and GTP remained significantly low. All hearts failed completely to recover cardiac pump function. The addition of glutamate to the perfusate during low-flow ischaemia had no significant effect on myocardial high-energy phosphates (HEP) but slightly increased succinate production. Subsequent reperfusion without added glutamate resulted in the recovery of 62% of pre-ischaemic aortic flow rate, as well as restoration of myocardial ATP and GTP to 70% of their control values and of creatine phosphate to supranormal levels. Reperfusion with added glutamate did not raise HEP levels any further but did increase recovery of cardiac function to 92% or more of pre-ischaemic values. Thus, by mechanism(s) which are not yet clear but which may include an increase in HEP via anaerobic succinate production, elevated levels of exogenous glutamate exert a highly beneficial effect on the post-ischaemic recovery of cardiac function.

Topics: Adenine Nucleotides; Animals; Blood Pressure; Coronary Circulation; Coronary Disease; Energy Metabolism; Glutamates; Glutamic Acid; Guanosine Triphosphate; Heart; Heart Rate; Male; Myocardium; Perfusion; Phosphocreatine; Rats; Rats, Inbred Strains; Reference Values

The effect of phosphocreatine and phosphocreatinine disodium salts on excitation conduction in acute myocardial ischemia was investigated, using repeated short-term ischemia exposures of the isolated rabbit ventricular septum as a model. Considerable improvement of excitation conduction through ischemized myocardium, seen after the administration of phosphocreatine and phosphocreatinine salts, was shown to be associated with Na+ added to the perfusion medium. Phosphocreatine and phosphocreatinine effects on excitation conduction time and the septal force in control perfusion were related to both the addition of Na+ and the binding of Ca2+ by these agents in the perfusion medium.

Topics: Acute Disease; Animals; Arrhythmias, Cardiac; Calcium; Coronary Disease; Culture Media; Electric Stimulation; Heart Conduction System; In Vitro Techniques; Male; Phosphocreatine; Rabbits; Sodium

The subcellular compartmentalization of adenosine 5'-triphosphate (ATP) in isolated perfused rat heart and its relation to energy depletion in ischemia were examined by 31P nuclear magnetic resonance (31P-NMR) spectroscopy and chemical analyses. The signal intensities of the beta-phosphate of ATP and creatine phosphate in the 31P-NMR were standardized by the intracellular volume ratio measured with 23Na-NMR to determine the actual content of each. During aerobic perfusion the ATP content determined by NMR (13.7 +/- 2.2 mumol/g dry weight) was significantly lower than that found by chemical analysis (22.4 +/- 0.7 mumol/g dry weight), while the creatine phosphate contents determined by the two methods were the same. During ischemia at 33 degrees C, the signal of the beta-phosphate of ATP in the 31P-NMR spectrum decreased progressively, disappearing completely after 16 min. But at this time 5.7 +/- 1.7 mumol/g dry weight of myocardial ATP was still detected by chemical analysis. These results indicated that there were two different compartments of intracellular ATP in the heart, only one of which is detectable by 31P-NMR spectroscopy, and that during ischemia the ATP that is detectable, which seems to be the free ATP in the cytosol, decreased more rapidly than the ATP in the other compartment.

Topics: Adenosine Triphosphate; Aerobiosis; Anaerobiosis; Animals; Coronary Disease; In Vitro Techniques; Magnetic Resonance Spectroscopy; Male; Myocardium; Phosphocreatine; Phosphorus; Rats; Rats, Inbred Strains; Reference Values

The in vivo oxidation of perfused [14C]-labeled fatty acids has been shown to decrease dramatically in hypoxic hearts. This study addresses the influence of ischemia and reperfusion on the enzymic activities of beta-oxidation of fatty acids in mitochondria and of peroxisomal origin. The rate of beta-oxidation of fatty acids in the isolated mitochondria from myocardium of swine fed control diet declined about 20% by the ischemic insult induced by hypothermic cardioplegic arrest. Upon reperfusion, the rate of mitochondrial beta-oxidation returned to a normal level. In clofibrate-fed animals, the rate of mitochondrial beta-oxidation did not vary significantly between control, ischemic, and perfused tissues. Furthermore, neither in control nor in clofibrate-fed animals did the rates of peroxisomal beta-oxidation of fatty acids vary significantly in the ischemic or reperfused tissues as compared to that of preischemic controls. These results suggest that ischemia does not contribute to any loss of enzymic activity in beta-oxidation of fatty acid cycles either in mitochondria or peroxisomes. Furthermore, the feeding of 0.5% (w/w) clofibrate to pigs increased the rate of mitochondrial beta-oxidation of fatty acids only by 50% while that of peroxisomes increased threefold. A similar threefold increase in catalase activity was also produced by clofibrate feeding. These results suggest that the heart plays a role in the hypolipidemic action of clofibrate.

Topics: Animals; Catalase; Clofibrate; Coronary Disease; Creatine Kinase; Fatty Acids; Heart Arrest, Induced; Microbodies; Mitochondria, Heart; Myocardial Reperfusion; Oxidation-Reduction; Phosphocreatine; Swine

To study the character of the mechanism of protective action of phosphocreatine on ischemic myocardium the effects of phosphocreatine (PCr) and phosphoarginine (PArg) were compared. PCr and PArg were shown to expose identical Ca2+-chelating properties and were used as their Na-salts. Only PCr protected the cardia function during ischemia and simultaneously inhibited the accumulation of lysophosphoglycerides, products of phospholipid degradation. PArg failed to exert both of these effects. By an EPR probe method PCr was shown to increase the order of structural organization of phospholipids in the cardiac sarcolemmal vesicles. The results show that the effect of PCr on ischemic myocardium is not due to nonspecific changes in the ion composition of a solution, but most probably due to highly specific effect of phosphocreatine on the phospholipid membrane of the cardiac cells sarcolemma.

Topics: Animals; Arginine; Cardiac Catheterization; Cats; Coronary Disease; Drug Evaluation, Preclinical; Heart; Hemodynamics; Lysophospholipids; Male; Myocardium; Organophosphorus Compounds; Phosphocreatine; Phospholipids; Rats; Rats, Inbred Strains; Spin Labels

Using isotope-labeled microspheres (diameter 15 microns) it was shown that phosphocreatine at a dose of 300 mg/kg does not affect the myocardial blood flow in the ischemic zone during acute occlusion (5 min) of the left anterior descending coronary artery (LAD) in dogs. Intravenous administration of NaCl hypertonic solution which contained the same amount of Na+ as 300 mg/kg of phosphocreatinine disodium salt prevented the development of ventricular fibrillation during acute LAD occlusion in dogs. Under these conditions excitation conduction velocity significantly increased. Experiments in isolated intraventricular rabbit septum have showed that the addition of phosphocreatine or phosphocreatinine to the perfusion medium at a concentration of 10 mmole/liter increased excitation conduction velocity in ischemic myocardium. However, when changes in perfusate Na+ and Ca2+ concentration produced by addition of phosphocreatine or phosphocreatinine were compensated, these compounds do not affect excitation conduction velocity. On the other hand, the alterations similar to those produced by the addition of phosphocreatine or phosphocreatinine led to the same increase of excitation conduction velocity. The results obtained indicate an important role of the changes of blood plasma ionic composition on intravenous administration of phosphocreatine in electrophysiological and antiarrhythmic effects of this substance during acute myocardial ischemia.

Topics: Acute Disease; Animals; Blood Pressure; Calcium; Coronary Circulation; Coronary Disease; Coronary Vessels; Dogs; Heart; Heart Rate; In Vitro Techniques; Myocardial Contraction; Phosphocreatine; Reference Values; Sodium

The effect of cibenzoline, an antiarrhythmic drug, on myocardial ischemia was studied in the anesthetized open-chest dog. Ischemia was induced by completely ligating or partially occluding the left anterior descending coronary artery. The levels of ATP and creatine-phosphate decreased, and the ADP and AMP levels increased during ischemia. The level of glycogen was also decreased, and that of lactate was increased by ischemia, resulting in myocardial acidosis. Pretreatment with either 2 mg/kg or 8 mg/kg of cibenzoline prevented the decrease in ATP level and the increase in lactate level. These results suggest that cibenzoline reduces the influence of ischemia on the myocardium.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Anti-Arrhythmia Agents; Coronary Disease; Dogs; Female; Glycogen; Hydrogen-Ion Concentration; Imidazoles; Male; Myocardium; Phosphocreatine

The effect of depletion of energy stores of rat hearts on their resistance to a total of 25 min ischemia was investigated by using a 31P-NMR method. Three experimental groups were compared: (1) pyruvate-perfused hearts depleted of adenine nucleotides (35% of normal) by 2-deoxyglucose (DG) treatment and containing deoxyglucose-6-phosphate (c. 40 mumol/g dry wt); (2) hearts partially depleted of glycogen stores (40 to 50% of initial) by long-term (2h) perfusion with pyruvate; (3) glucose perfused (11 nM) hearts with normal ATP and glycogen contents. By the end of ischemia the intracellular pH was decreased by 0.33, 0.90 and 1.40 units, respectively. Time to peak of ischemic contracture increased in this series from 3 to 18 and 24 min, respectively. At the peak of ischemic contracture ATP content was c. 30 to 40% (6 to 8 mumol/g dry wt) of normal value in all three groups. Reperfusion of hearts resulted in development of significant reperfusion contracture in glucose-perfused hearts and minor contracture in other series. Recovery of high energy phosphates and cardiac work index in DG-treated, glycogen-depleted and glucose-perfused hearts were: for phosphocreatine (PCr), 72, 102 and 83%; for ATP, 29, 47 and 56% and for cardiac work, 66, 78 and 24%, respectively. Recovery of cardiac work did not correlate linearly with tissue ATP. These data demonstrate that post-ischemic recovery of the contractile function of isovolumic heart may be dissociated from pre-ischemic myocardial ATP and glycogen contents. This dissociation can be explained by the two major factors: (1) the contribution of ischemic acidosis and catabolites accumulation to the cell damage and (2) by ATP compartmentation.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Deoxy Sugars; Deoxyglucose; Glucose; Glucose-6-Phosphate; Glucosephosphates; Glycogen; Magnetic Resonance Spectroscopy; Male; Myocardial Contraction; Myocardium; Perfusion; Phosphocreatine; Pyruvates; Rats; Rats, Inbred Strains; Time Factors

A comparison between the protective activity of bepridil, its novel derivative, CERM 11956, and nifedipine in isolated electrically paced guinea-pig hearts after 60 min of global ischaemia followed by 30 min of reperfusion has been made. All three compounds exerted a significant anti-ischaemic effect, as indicated by an improved recovery of functional parameters (left ventricular pressure and coronary perfusion), a delayed onset of the ischaemic contracture, and an enhanced recovery of biochemical (CrP, ATP and adenylate energy charge) parameters. The most pronounced anti-ischaemic activity was shown by the compound CERM 11956 at concentrations that displayed only minor negative inotropic activity. From the results it may be concluded that the new bepridil derivative, CERM 11956, is a promising and potent anti-ischaemic compound, which has little influence on haemodynamic parameters.

Topics: Adenosine Triphosphate; Animals; Bepridil; Calcium Channel Blockers; Coronary Circulation; Coronary Disease; Female; Guinea Pigs; In Vitro Techniques; Male; Myocardial Contraction; Nifedipine; Phosphocreatine; Pyrrolidines

To investigate mechanisms of development in ischemic myocardial injury, intracellular pH and high energy phosphates in perfused guinea-pig hearts were monitored by 31P-MRS. Intracellular ATP content decreased to 1.2% and 26.4% of control during 60 minutes global ischemia, respectively with and without preischemic administration of isoproterenol. Intracellular pH declined to 6.48 and 6.03 respectively. Postischemic cardiac function was severely impaired by isoproterenol. ATP breakdown had little influence on intracellular pH in ischemic hearts. It was verified that inotropic agents can progress ischemic myocardial injury, and that contractile recovery is more correlated with the residual ATP level than intracellular pH.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Guinea Pigs; Heart; Hydrogen-Ion Concentration; Isoproterenol; Kinetics; Magnetic Resonance Spectroscopy; Male; Myocardium; Phosphates; Phosphocreatine

The ATP and creatine phosphate (PCr) contents in isolated guinea-pig hearts were determined by 31P-MRS measurement at 80.75 MHz using the Langendorff technique. Reperfusion of post-ischemic hearts with adenosine for 180 minutes increased ATP to 117.4% and decreased PCr to 59.8% of the preischemic value. Reperfusion without adenosine did not increase ATP and did not decrease PCr. The depressed cardiac function due to ischemia was remarkably improved in post-ischemic hearts by the increase in ATP due to adenosine. We found that the loss of ATP due to ischemia is not necessarily proportional to the extent of myocardial ischemic injury.

Topics: Adenosine; Adenosine Triphosphate; Animals; Coronary Disease; Guinea Pigs; Heart; In Vitro Techniques; Kinetics; Magnetic Resonance Spectroscopy; Male; Myocardium; Perfusion; Phosphocreatine; Phosphorus

Perfused guinea-pig hearts, which were analyzed by 31P-MRS, were subjected to 30 and 60 minute ischemia and reperfused using two perfusates, one containing 200 microM inosine, and the other without inosine. After 4 hour reperfusion with inosine, ATP levels increased to 95.5% of preischemic value (30 minute ischemia) and 76.2% (60 minute ischemia). However, after 4 hour reperfusion without inosine, ATP levels increased only to 72.2% (30 minute ischemia) and to 48.2% (60 minute ischemia). In 60 minute ischemic hearts reperfused with inosine, left ventricular maximal positive dp/dt (LV dp/dt) was improved significantly to 82.4% after 6 hour reperfusion in contrast to hearts reperfused without inosine (43.1%). Administration of inosine was very useful for increasing myocardial gross energy product and improving cardiac performance.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Energy Metabolism; Guinea Pigs; Heart; Hydrogen-Ion Concentration; Inosine; Magnetic Resonance Spectroscopy; Male; Perfusion; Phosphocreatine; Time Factors

A study was undertaken to examine the effects of glucose versus pyruvate as the sole substrate following severe myocardial ischemia. Glycolysis usually contributes only a small amount to total ATP production and may be rate limiting in providing tricarboxylic acid (TCA) cycle substrates. Consequently, pyruvate may be a more effective substrate by bypassing glycolysis to feed directly to the TCA cycle and oxidative phosphorylation. Isolated rat hearts were studied in a retrograde (Langendorff) perfusion apparatus while in an NMR spectrometer. Rate pressure product (RPP), myocardial oxygen consumption (MVO2), and the unidirectional Pi----ATP rate were measured in control and postischemic hearts with or without the inotrope dobutamine. The undirectional Pi----ATP rate was higher in the glucose than the pyruvate hearts and the difference increased further postischemia. This increase over that of the pyruvate hearts has been attributed to a glycolytic component of ATP metabolism. Oxygen consumption was higher in pyruvate hearts at equivalent levels of performance. It thus appears that the glycolysis rate is significant and may be elevated following severe myocardial ischemia. Perfusion with pyruvate requires increased rates of oxidative phosphorylation to make up for the loss of glycolytically produced ATP. Optimal postischemic substrate delivery may require several compounds, one of which should be glucose.

Topics: Adenosine Triphosphate; Animals; Biomechanical Phenomena; Blood Pressure; Coronary Disease; Heart; Heart Rate; Myocardium; Osmolar Concentration; Phosphates; Phosphocreatine

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Energy Metabolism; In Vitro Techniques; Magnetic Resonance Imaging; Myocardial Contraction; Myocardium; Perfusion; Phosphocreatine; Rats; Rats, Inbred Strains

The effects of total ischemia and subsequent reperfusion on the formation of anaerobic metabolism products and their release into myocardial effluent were studied in isolated guinea pig hearts. During 30-min ischemia myocardial ATP and phosphocreatine decreased to 34 and 15% of the initial levels, respectively; this was accompanied by alanine formation and approximately stoichiometric glutamate loss. The increase in malate in ischemic myocardium corresponded to the anaplerotic flux aspartate----oxaloacetate----malate; the succinate production being commensurable to alpha-ketoglutarate formation in the alanine aminotransferase reaction. The release of lactate, alanine, succinate, creatine and pyruvate trace amounts into the myocardial effluent was observed during an early phase of the reperfusion using 1H-NMR. The rates of metabolite release reduced as follows: lactate much greater than alanine greater than succinate greater than creatine. By the 30th min of the reperfusion the decrease in these metabolites tissue contents was accompanied by the recovery of ATP and phosphocreatine levels up to 65 and 90% of the initial ones, respectively. The data obtained demonstrate that the formation and the release of succinate, alanine and creatine from the heart as well as of lactate may indicate profound disturbances in energy metabolism.

Topics: Adenine Nucleotides; Anaerobiosis; Animals; Aspartic Acid; Citric Acid Cycle; Coronary Disease; Glutamates; Glycolysis; Guinea Pigs; Lactates; Magnetic Resonance Spectroscopy; Myocardial Infarction; Perfusion; Phosphocreatine

Hyperemic flow occurs after release of a transient coronary artery occlusion in excess of the acquired oxygen debt if the vessel has sufficient vasodilator reserve. The purpose of this study was to determine whether differences exist in the degree of postischemic functional and metabolic recovery in the stunned myocardium when a reactive hyperemia is allowed to occur as opposed to reperfusion in the presence of a flow-limiting coronary artery stenosis. Anesthetized dogs were subjected to 15-minute episodes of coronary artery occlusion, followed by either 10 minutes (short reperfusion) or 3 hours (long reperfusion) of reperfusion to investigate early and late differences in tissue blood flow. At reperfusion a micrometer-driven occluder was either released fully within 1 minute (full-reactive [FR] group) or the occluder was slowly released to return coronary blood flow to preocclusion levels (no-reactive [NR] group). Areas at risk, myocardial blood flow (radioactive microspheres), hemodynamics, myocardial segment shortening (sonomicrometry) during occlusion, and high-energy phosphate levels (tissue biopsies) at 3 hours of reperfusion were similar in both groups. Recovery of function in the short-reperfusion group was significantly greater in the FR than the NR group until 3 minutes of reperfusion, which corresponded to the peak reactive hyperemic response. After this time there were no differences between the two groups in functional recovery until 2 and 3 hours after reperfusion when the percentage of segment shortening had deteriorated to a significantly greater extent (p less than 0.05) in the NR group than in the FR group. The reason for this finding may involve prolonged subendocardial ischemia if reperfusion is introduced into a flow-limiting stenosis, as suggested by the greater tissue blood flows in the ischemic reperfused region during early reperfusion in the FR versus NR group. These data suggest that coronary artery patency, in part, determines functional recovery in the stunned myocardium.

Topics: Adenine Nucleotides; Animals; Blood Pressure; Coronary Circulation; Coronary Disease; Coronary Vessels; Dogs; Heart Rate; Myocardium; Phosphocreatine; Time Factors

We attempted to identify the nature and time-course of metabolic changes occurring during ischaemia followed by reperfusion either in coronary artery disease patients undergoing intracoronary thrombolysis or in isolated and perfused rabbit hearts. Arterial and coronary sinus differences for oxygen, lactate, glucose, free fatty acid and creatine kinase were measured in patients undergoing successful intracoronary thrombolysis of left anterior descending occlusion. Early reperfusion (after 160 mins of ischaemia) restored aerobic metabolism and myocardial contractility. In contrast, reperfusion after more prolonged ischaemia (335 mins) did not restore mitochondrial function or contractile activity of the myocytes. Results obtained using isolated and perfused rabbit hearts also confirm that the likelihood of recovery during reperfusion depends on the rapidity of recanalization. Furthermore the data reported indicate that on reperfusion after prolonged ischaemia (90 mins) cell damage occurs, leading to a breakdown of the permeability barrier to ions and to larger molecules such as creatine phosphokinase. As a consequence, reperfusion produces a large increase of intracellular calcium, whilst the intracellular magnesium content is severely reduced. Under these conditions, with the observed loss of magnesium from the cell, mitochondrial calcium transport is highly stimulated and the equilibrium between ATP synthesis and calcium influx is shifted towards calcium influx. This sequence of events leads to mitochondrial calcium overload with subsequent damage of mitochondrial structure and loss of the ability to synthesize ATP. Reperfusion of the isolated rabbit hearts with solutions containing high magnesium and low calcium for 10 mins reduced mitochondrial calcium overload. This, in turn, resulted in maintenance of ATP synthesis and, on return to normal perfusate, in partial recovery of developed pressure and myocardial ATP content. These findings may be of importance in the restoration of blood flow to ischaemic heart muscle during thrombolysis.

Topics: Adenosine Triphosphate; Animals; Calcium; Coronary Circulation; Coronary Disease; Fibrinolysis; Humans; In Vitro Techniques; Magnesium; Myocardium; Phosphocreatine; Rabbits

Phosphorus-31 magnetic resonance spectroscopy was used to study the relationship between metabolic and functional alterations during acute regional ischemia in vivo. Phosphocreatine, adenosine triphosphate (ATP), inorganic phosphate, and intracellular pH (pHi) were monitored in 11 pigs at 2-minute intervals during 4 and 20 minutes of acute left anterior descending coronary artery occlusion followed by 20 minutes of reperfusion. In a parallel series of experiments, segment shortening was continuously monitored by sonomicrometry during the early ischemic period. Segment shortening decreased precipitously after coronary occlusion, and systolic expansion was noted within 30 seconds. Phosphocreatine levels decreased rapidly and reached a minimum value of 44 +/- 13% (mean +/- SE) of the control value by 20 minutes of ischemia. Ischemia-induced reduction of ATP was small and not statistically significant. Inorganic phosphate increased rapidly to a peak level of 158 +/- 9% of the control value by 4 minutes of ischemia. Intracellular pH decreased 0.76 +/- 0.04 units during the initial 10 minutes of ischemia and subsequently stabilized. After reperfusion, phosphocreatine, inorganic phosphate, and pHi recovery occurred within 4 minutes and was similar in the 4- and 20- minute ischemia groups. These results indicate that the changes in high-energy phosphates and pHi observed during both 4 and 20 minutes of coronary occlusion are rapidly reversible. The temporal course of metabolic and functional alterations during early ischemia suggests that if these are causally related the decline in contractility is mediated by an increase in inorganic phosphate, a decrease in pHi, or both rather than by loss of ATP.

Topics: Adenosine Triphosphate; Animals; Biopsy; Constriction; Coronary Disease; Coronary Vessels; Disease Models, Animal; Hemodynamics; Hydrogen-Ion Concentration; Intracellular Fluid; Magnetic Resonance Spectroscopy; Myocardial Contraction; Myocardium; Perfusion; Phosphates; Phosphocreatine; Phosphorus Isotopes; Swine

Effects of iloprost on the behaviour of high energy phosphate contents were investigated in global ischemic and reperfused rat hearts prepared according to Langendorff. Iloprost application before and after 20 min of ischemia at a dosage of 9-12 pg/g heart weight x min improved the availability of high energy phosphates as was shown by CP/Pi ratio during the first hour of reperfusion.

Topics: Animals; Coronary Disease; Epoprostenol; Heart; Iloprost; In Vitro Techniques; Magnetic Resonance Spectroscopy; Male; Myocardium; Perfusion; Phosphates; Phosphocreatine; Rats; Rats, Inbred Strains

During prolonged ischemic cardiac arrest successful myocardial protection depends upon uniform delivery of cardioplegic solutions to all regions of the heart. Accordingly, we studied the regional and transmural distribution of a neutral crystalloid (dextran-saline) solution during normothermic (37 degrees C) ischemia in 18 isolated blood-perfused dog hearts (isovolumic left ventricle). In the baseline state, coronary perfusion pressure was 100 mmHg. At the onset of ischemia and every 15 min throughout ischemia, we infused 100 ml of crystalloid solution (37 degrees C) at a perfusion pressure of 100 mmHg and the distribution of crystalloid solution was assessed (radioactive microsphere technique). The hearts were reperfused after 60 min (n = 9) or 90 mins (n = 9) of ischemia. In the baseline pre-arrest state the left ventricle (LV) received 67 +/- 1.0% of the total coronary blood flow; the LV subendocardial to subepicardial flow ratio was 1.33 +/- 0.18, the LV end diastolic pressure was 7.5 +/- 0.4 mmHg, and mean transmural myocardial adenosine triphosphate (ATP) was 16.4 +/- 1.1 microM/g DW. At the onset and throughout the first 45 mins of ischemia (n = 9), regional and transmural distribution of the crystalloid solution was similar to that of coronary blood flow during the baseline state; there was no change in LV end diastolic pressure, but there was a moderate fall in ATP content (7.26 +/- 1.6 micron/g DW). After 75 mins of ischemia (n = 9), despite the development of ischemic contracture (LV end diastolic pressure exceeded 20 mmHg in all 9 hearts) and marked ATP depletion (2.76 +/- 0.5 microM/g DW), there was an increase in crystalloid solution delivery to the LV as a whole and the subendocardium in particular (the LV received 82 +/- 2.0% and the subendocardial to subepicardial flow ratio was 1.75 +/- 0.1). Even in a subgroup with severe contracture during ischemic arrest (LV end diastolic pressure greater than 60 mmHg, n = 4) there was no reduction in crystalloid solution delivery. Thus, the presence of ischemic contracture does not preclude delivery of crystalloid solution to the LV subendocardium.

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Coronary Circulation; Coronary Disease; Dextrans; Dogs; Energy Metabolism; Heart; Heart Arrest; Heart Ventricles; In Vitro Techniques; Lactates; Myocardial Contraction; Oxygen Consumption; Perfusion; Phosphocreatine; Ventricular Function

The excessive gain in Ca2+ that occurs when hearts are reperfused after prolonged periods of ischemia contributes to cell death and tissue necrosis. The following experiments were undertaken to determine whether nicotine, in a concentration equivalent to the peak concentration present in plasma after cigarette smoke inhalation, alters reperfusion-induced Ca2+ gain in isolated rat hearts. Nicotine (0.15 microgram/ml) failed to increase tissue Ca2+ during aerobic perfusion but increased Ca2+ gain during reperfusion after 30 (p less than 0.02) or 60 (p less than 0.02) min of normothermic ischemia. The increase of Ca2+ gain was independent of a nicotine-induced release of norepinephrine (NE) or an altered "reflow area", heart rate, force of contraction, or end-diastolic resting tension. Pretreatment for 3 days with anipamil (20 mg/kg), a long-acting calcium channel blocker, attenuated the reperfusion-induced Ca2+ gain after 30 min of global ischemia, and reduced (p less than 0.001) the nicotine-induced exacerbation of that gain, without altering tissue ATP or creatine phosphate (CP). Verapamil (1 X 10(-6) M) reduced (p less than 0.02) the nicotine-induced exacerbation of Ca2+ gain caused by reperfusion after 30 min of ischemia.

Topics: Adenosine Triphosphate; Animals; Calcium; Calcium Channel Blockers; Coronary Circulation; Coronary Disease; Female; Heart Rate; In Vitro Techniques; Nicotine; Norepinephrine; Perfusion; Phosphocreatine; Propylamines; Rats; Rats, Inbred Strains

Reperfusion of ischemic myocardium has been postulated to result in a specific oxygen radical-mediated component of tissue injury. In a previous study we demonstrated improved recovery of ventricular function and metabolism when the superoxide radical scavenger superoxide dismutase was administered at the time of postischemic reflow. Studies in vitro, have suggested that superoxide toxicity might be mediated via the generation of more reactive hydroxyl radicals in an iron-catalyzed reaction. The present study was designed to test the hypothesis that myocardial reperfusion injury might be reduced by administration of the iron chelator deferoxamine at the time of reflow, most likely by preventing hydroxyl radical formation. Sixteen isolated Langendorff rabbit hearts, perfused within the bore of a superconducting magnet, were subjected to 30 min of normothermic (37 degrees C) total global ischemia followed by 45 min of reperfusion. At reflow eight treated hearts received a 10 ml bolus containing 50 mumol of deferoxamine followed by an infusion of 11 mumol/min for the first 15 min of reflow. The hearts were then perfused with standard perfusate for an additional 30 min. Eight untreated control hearts received a similar bolus of perfusate followed by 45 min of standard reperfusion. Serial 5 min 31P nuclear magnetic resonance spectra were recorded. Myocardial phosphocreatine (PCr) content fell to 5% to 7% of control during ischemia in both groups of hearts. Deferoxamine-treated hearts recovered 99 +/- 10% of control PCr content, while untreated hearts recovered 60 +/- 16% (p less than .05). Intracellular pH fell to 5.9 during ischemia in both groups, before showing more rapid and complete recovery in treated hearts (p less than .01). Recovery of developed pressure reached 70 +/- 6% of control in treated hearts compared with 35 +/- 10% in untreated hearts (p less than .05). Iron content of the perfusate was 7 microM, and by electron paramagnetic resonance spectroscopy was in the form of Fe3+-EDTA complexes. In the effluent of treated hearts iron was in the form of Fe3+-deferoxamine chelates. In summary, administration of the iron chelator deferoxamine at the time of postischemic reflow results in greater recovery of myocardial function and energy metabolism, which supports the hypothesis that iron plays an important role in the pathogenesis of reperfusion injury.

Topics: Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Deferoxamine; Electron Spin Resonance Spectroscopy; Female; Free Radicals; Iron; Iron Chelating Agents; Myocardium; Oxygen; Perfusion; Phosphocreatine; Rabbits

Xanthine oxidase (XO) has been hypothesized to be a potential source of oxygen-derived free radicals during reperfusion of ischemic myocardium based on the fact that allopurinol, a XO-inhibitor, can reduce reperfusion injury. In this communication we report that both allopurinol and oxypurinol, the principle metabolite of allopurinol, prevent the reperfusion injury in isolated pig heart. However, we found that neither pig heart nor pig blood contain any XO activity. Our study showed a direct free radical scavenging action of these XO-inhibitors during ischemia and reperfusion, as judged by the reduction of free radical signals when compared using an Electron Paramagnetic Resonance Spectrometer. Using a Luminometer, we also confirmed that both allopurinol and oxypurinol can scavenge ClO2, HOCl, and significantly inhibit free radical signals generated by activated neutrophils. These XO-inhibitors, however, failed to scavenge O2. and OH. radicals. Our results suggest that these XO-inhibitors salvaged the ischemic-reperfused myocardium by scavenging free radicals, and not by inhibiting XO in the pig heart.

Topics: Adenosine Triphosphate; Allopurinol; Animals; Coronary Disease; Female; Free Radicals; Heart; Hydroxides; Hydroxyl Radical; Hypoxanthine; Hypoxanthines; Male; Myocardium; Oxypurinol; Phosphocreatine; Pyrimidines; Swine; Xanthine; Xanthine Oxidase; Xanthines

The effect of nadolol at a dose of 1 mg kg-1, i.v. on the ischaemic myocardial metabolism has been examined in the dog. Ischaemia was induced by ligating the left anterior descending coronary artery for 3 min, and nadolol was injected 5 min before ligation. Ischaemia caused myocardial metabolic changes; it decreased energy charge potential and inhibited glycolytic flux through phosphofructokinase reaction. Pretreatment with nadolol lessened the decrease in energy charge potential and the inhibition of glycolytic flux being caused by ischaemia. Nadolol may have a beneficial effect on the ischaemic myocardium.

Topics: Adenine Nucleotides; Animals; Carbohydrate Metabolism; Coronary Disease; Dogs; Energy Metabolism; Female; Heart; Hemodynamics; Hexosephosphates; Male; Myocardium; Nadolol; Phosphocreatine

The changes in the contents of the main tricarboxylic acid cycle intermediates and related amino acids under total ischemia and subsequent reperfusion of isolated guinea pig heart were studied. The decrease in ATP and phosphocreatine during 30 min ischemia was accompanied by alanine formation and approximately stoichiometric glutamate loss. The increase in malate in ischemic myocardium corresponded to the anaplerotic flux aspartate----oxaloacetate----malate. The succinate production was commensurable to alpha-ketoglutarate formation in the alanine aminotransferase reaction. The release of bulk amount of lactate, alanine and succinate into the myocardial effluent was observed during an early phase of the reperfusion using 1H NMR. In contrast to these metabolites, malate release was not observed in the reperfusion. By the 30th min of the reperfusion the decrease in lactate, alanine, malate and succinate tissue contents to the preischemic values was accompanied by the recovery of ATP and phosphocreatine. The results suggest that the formation and the release of succinate and alanine from the heart, complementary to that of lactate, reflect profound disturbances in energy metabolism.

Topics: Adenosine Triphosphate; Alanine; Amino Acids; Animals; Citric Acid Cycle; Coronary Disease; Glutamates; Glutamic Acid; Guinea Pigs; In Vitro Techniques; Myocardium; Perfusion; Phosphocreatine

Topics: Aged; Coronary Disease; Drug Evaluation; Electrocardiography; Exercise Test; Humans; Male; Middle Aged; Phosphocreatine

We determined the time course of ischemic injury, the effects of reperfusion, and the protective effects of prostacyclin, oxygen radical scavengers, and diltiazem on myocardial myocyte and endothelial cell functions in isolated rat hearts. Left ventricular power and coronary microvascular permeability were used as indexes of myocyte and endothelial cell function, respectively. Neither 5- nor 10-min ischemia reperfusion significantly changed power or permeability. However, with reperfusion following 20 and 30 min of ischemia, power was reduced 50 and 60% and permeability increased 70 and 90%. In 30-min ischemic hearts the ischemia-induced increase in permeability was apparent after 4 min reperfusion and further exacerbated at 20 min. Hypoxic reperfusion did not prevent increased permeability. Prostacyclin or a combination of superoxide dismutase, catalase, and mannitol also did not prevent increased permeability, and the radical scavengers did not ameliorate depressed power. In contrast, perfusion with diltiazem during ischemia reperfusion blunted the reduction in power and prevented the increase in permeability. We conclude that ischemia reperfusion causes similar time course of injury to myocytes and endothelial cells; reperfusion contributes to endothelial injury, and diltiazem affords protection to both cell types.

Topics: Adenosine Triphosphate; Animals; Capillary Permeability; Catalase; Coronary Circulation; Coronary Disease; Diltiazem; Endothelium; Epoprostenol; Male; Mannitol; Muscles; Phosphocreatine; Rats; Rats, Inbred Strains; Superoxide Dismutase

Topics: Adenine Nucleotides; Alanine; Animals; beta-Alanine; Coronary Disease; Heart; Male; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains; Taurine

The influence of verapamil (V) and of V combined with glucose-insulin-potassium (VG) on ischemic injured myocardium was investigated in dogs after ligation of the left anterior descending coronary artery. Three hours after coronary artery ligation with VG application during the last two hours the left ventricular end diastolic pressure (LVEDP) and the pressure rate product were decreased in contrast to the behaviour after V infusion. Contents of ATP and creatine phosphate were preserved in equal extent by V and VG, but the lowest content in inorganic phosphate was found in ischemic and nonischemic left ventricular tissue after VG application. Thus, VG seems to enable the tissue to save more effective energy rich phosphates and to contribute to the economization of cardiac work by reduction of preload.

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Cardioplegic Solutions; Coronary Disease; Dogs; Drug Therapy, Combination; Glucose; Insulin; Myocardium; Phosphates; Phosphocreatine; Potassium; Verapamil

To examine the effects of diltiazem on myocardial ischemia, 200 micrograms/kg of diltiazem were injected intravenously into anesthetized open-chest mongrel dogs 10 min after coronary ligation. This was followed by a continuous infusion of diltiazem at 10 micrograms/kg/min for 50 min. Regional myocardial blood flow (MBF) was measured by the hydrogen gas clearance method. Sixty minutes after ligation, myocardial specimens were taken from the areas where MBF was measured, and the ATP and CP contents were determined by the bioluminescence method. Simultaneously, mitochondria were isolated from the ischemic and nonischemic areas, and both the respiratory control index (RCI) and the rate of oxygen consumption in state III (QO2 III) were calculated. The aortic systolic pressure and heart rate of diltiazem treated and untreated dogs were not significantly different, and diltiazem did not increase the MBF in the area with a MBF below 40 ml/min/100 g. When MBF was 10 to 30 ml/min/100 g, the ATP content in the diltiazem treated hearts was significantly higher than that in the untreated dogs, whereas the CP content was not significantly changed. Thus, diltiazem administered after ischemia preserved ATP content in the ischemic myocardium with a MBF of 10 to 30 ml/min/100 g without significantly affecting the hemodynamics or MBF. This suggests that diltiazem exerts a cardioprotective effect by acting directly on the ischemic myocardium if it has an MBF above a certain level, even when the drug is administered after the onset of ischemia.

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Coronary Circulation; Coronary Disease; Diltiazem; Dogs; Energy Metabolism; Female; Ligation; Male; Mitochondria, Heart; Myocardium; Phosphocreatine

Hearts from rats, which received high doses of furosemide alone or the same doses of furosemide plus amiloride in a diet with low magnesium content for 4 weeks, were isolated and perfused in the Langendorff mode. After 15 min. of normoxic control perfusion no differences were found between the two groups of hearts with respect to cardiac physiology. After 20 min. of subtotal, global ischaemia and 15 min. of reperfusion the furosemide plus amiloride hearts showed a significantly higher recovery of function (judged by pressure rate product and coronary flow rate) than furosemide hearts. However, the myocardial content of adenosine triphosphate, creatine phosphate, and electrolytes at the end of the experiment exhibited no difference between the two groups. In separate experiments it was found that the addition of amiloride to the furosemide regimen significantly raised and almost normalized the values of plasma magnesium and potassium. Myocardial calcium was lower, whereas the magnesium and potassium content in the hearts was not different from the furosemide group. It is concluded that the administration of amiloride to rats provided high doses of furosemide and marginal magnesium supplies afforded some protection upon the ischaemic heart.

Topics: Adenosine Triphosphate; Amiloride; Animals; Coronary Circulation; Coronary Disease; Diuretics; Electrolytes; Furosemide; Heart; Male; Perfusion; Phosphocreatine; Rats; Rats, Inbred Strains

The effect of cellular creatine (Cr) and adenine nucleotides (AdN) deficiency on cardiac work, ATP turnover rate and flux through creatine kinase (CK) has been investigated. Depletion of 60-65% of total heart AdN by 2-deoxyglucose treatment in the presence of pyruvate and subsequent washout resulted in only 25% decrease in contractile activity and phosphocreatine level. Substitution of 80-90% of heart Cr (and PCr) by guanidinopropionic acid (GP) by feeding of rats with 1% GP diet reduced maximal values of cardiac work, ATP turnover and flux through CK by 40-50% and elevated end diastolic pressure and index of diastolic stiffness. Hearts depleted of AdN or glycogen showed better post-ischemic recovery of mechanical function that can be attributed to restriction of accumulation of ischemic catabolytes (lactate, H+, Pi). These data imply that in myocardium PCr is an essential high energy phosphate and contractile function stays unchanged at significantly reduced ATP levels.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Creatine Kinase; In Vitro Techniques; Myocardial Contraction; Myocardium; Perfusion; Phosphocreatine; Rats

After prolonged ischemia followed by reperfusion of the isolated rat heart, irreversible heart failure is associated with creatine kinase leakage from the cells. The possible implications of MM creatine kinase leakage from myofibrillar compartments on the contractile properties of ventricular muscle have been studied in control versus ischemic hearts. Total creatine kinase activity decreased in ischemic cells while creatine kinase and ATPase activities were not modified in isolated myofibrils. The efficiency of creatine kinase and phosphocreatine in the relaxation of rigor tension in skinned ventricular preparations was not changed after ischemia. Furthermore, neither the pCa/tension relationship nor the rate of tension development following length changes were modified by ischemia. These results show that the contractile properties of myofilaments as well as the functional coupling between myosin ATPase and creatine kinase are preserved in ischemic hearts suffering irreversible contractile failure.

Topics: Adenosine Triphosphate; Animals; Calcium; Coronary Disease; Creatine Kinase; In Vitro Techniques; Muscle Relaxation; Myocardial Contraction; Myocardium; Octoxynol; Papillary Muscles; Phosphocreatine; Polyethylene Glycols; Rats

Impaired energy production has been proposed as one mechanism to explain the contractile abnormality in post-ischemic "stunned" myocardium. If energy production were impaired, administration of inotropic agents should result in a deterioration of cellular energy stores because of an inability of ATP synthesis to match the rate of increased utilization. In this study we correlated changes in myocardial high energy phosphates, measured by 31P-NMR spectroscopy, with changes in left ventricular function and energy requirement in buffer perfused rabbit hearts following ischemia and reperfusion, and during stimulation with isoproterenol. Hearts were stunned by 20 min of zero flow global ischemia at room temperature. After reperfusion, isovolumic developed pressure returned to 77.8 +/- 2.2% of baseline and ATP content was reduced to 80.9 +/- 4.1% of baseline. Isoproterenol (5 x 10(-8) M for 10 min) caused increases in developed pressure and rate-pressure product (to 134.1 +/- 12.6% and 195.0 +/- 21.4% of baseline, respectively) without a decrease in ATP or phosphocreatine (PCr) content (80.0 +/- 7.1% and 103.0 +/- 3.8% of preischemia, respectively), and without functional or metabolic deterioration of the hearts after discontinuation of the drug. Control hearts not subjected to ischemia showed similar functional and metabolic responses to isoproterenol. The phosphocreatine/inorganic phosphate (PCr/Pi) ratio, an index of the balance between energy production and utilization, was higher (not lower) than baseline in stunned hearts, thus confirming that energy production was not intrinsically impaired. Together these data indicate that despite reduced myocardial ATP content, mitochondrial function in stunned hearts is capable of sustaining a large increase in function and energetic requirements.

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Animals; Coronary Disease; Female; Heart; In Vitro Techniques; Microscopy, Electron; Myocardial Contraction; Myocardium; Phosphocreatine; Rabbits; Reference Values

Topics: Adenosine Triphosphate; Animals; Calcium; Catecholamines; Constriction; Coronary Disease; Coronary Vessels; Gallopamil; Heart; Hemodynamics; Mitochondria, Heart; Myocardium; Perfusion; Phosphocreatine; Rabbits

A new ion-pair reversed-phase high-performance liquid chromatography method was applied to simultaneous measurements of porcine myocardial adenine nucleotides and creatine phosphate. The homogeneity of each desired peak was tested by the retention times of standards, chromatography of spiked samples, the absorbance ratios at various wavelengths, and the differing retention times for a number of other compounds found in porcine myocardial extracts.

Topics: Adenine Nucleotides; Animals; Chromatography, High Pressure Liquid; Coronary Disease; Energy Metabolism; Myocardium; Phosphocreatine; Swine

The left anterior descending coronary artery was occluded for 22.5, 45, 90, 180, and 360 mins in anesthesized open-chest dogs and pigs and thereafter reperfused for 30 min. Myocardial oxygen consumption was varied in dogs by cholinergic stimulation (bradycardia) and by cutting of the right and left vagus nerve (tachycardia). Regional myocardial blood flow was measured with radioactive tracer microspheres at the end of the occlusion period and 5 and 30 min after reflow. Tissue content of adenine nucleotides and of phosphocreatine were determined in the subendo- and subepicardium of transmural biopsies at the end of reflow. Infarct size was determined with nitrobluetetrazolium and compared with risk region size. Porcine hearts developed infarcts sooner. Those canines with a high MVO2 due to tachycardia had larger infarcts than those with bradycardia and resembled infarct development in the pig. The evolution of infarcts with time depended strongly on collateral flow which was significantly higher in canine hearts. Higher collateral flow and lower MVO2 in one group of canine hearts also resulted in better preserved tissue ATP. The fall in tissue ATP with time after coronary occlusion was compared with the O2-supply via collateral flow during occlusion. Assuming that the oxygen entering ischemic myocardium was used for ADP phosphorylation, we could estimate the degree of ATP-"overspending". Overspending was highest in low-flow ischemia and it correlated well with the speed of infarction. The ATP-data are best explained by the phosphocreatine energy shuttle model and by assuming slow access of cytosolic ATP to the ATP-splitting sites at the myofibrils. In conclusion, we postulate that both collateral flow as well as myocardial oxygen consumption before and during occlusion determine infarct size.

Topics: Adenine Nucleotides; Adenosine Triphosphate; Animals; Blood Pressure; Collateral Circulation; Coronary Circulation; Coronary Disease; Dogs; Female; Heart Rate; Male; Microspheres; Myocardial Infarction; Myocardium; Oxygen Consumption; Phosphocreatine; Swine

To characterize the temporal and spatial characteristics of transmural gradients of flow, ATP and CP, dogs (n = 17) were subjected to coronary artery ligation for either 30 minutes or 24 hours. Different radioactive microspheres were given at the onset and end of the ischemic period. Simultaneous multiple transmural biopsies (up to 20 per heart) were obtained (in situ freezing) from central ischemic and surrounding normal tissue after either 30 minutes or 24 hours of elapsed ischemia. After lyophilization each biopsy was divided into up to 6 transmural sub-fragments, each of which was analysed for flow, ATP and CP. At the onset of ischemia flow declined to less than 15% throughout the ischemic zone and there was a slight transmural gradient of flow from epi- to endocardium (12.4 +/- 1.6, 13.5 +/- 2.0, 11.0 +/- 1.8, 10.3 +/- 1.7, 8.5 +/- 1.9 and 8.3 +/- 3.1% of non-ischemic tissue). After 30 minutes of ischemia, collateral flow to the epicardial tissue had increased substantially but endocardial flow remained unchanged, the epi- to endo- gradient was 20.8 +/- 2.5, 18.9 +/- 2.4, 13.7 +/- 2.1, 10.8 +/- 1.5, 8.5 +/- 1.2, 7.6 +/- 1.7. After 24 hours there were further increases in the epi- and mid- myocardial regions but the endocardial flow remained severely depressed, the epi- to endo- gradient was 23.9 +/- 3.2, 24.5 +/- 3.0, 23.6 +/- 4.8, 16.4 +/- 3.3, 9.8 +/- 2.9, 5.8 +/- 2.9%. ATP and CP were severely depressed after 30 minutes of ischemia and reflected flow closely with sharp linear epi- to endo- gradients (17.5 to 10.9 muMol/g dry wt for ATP and 7.4 to 3.1 muMol/g dry wt for CP). After 24 hours, the decline in ATP had been slowed and there was a striking recovery of CP in the epi- and mid- myocardial regions which had experienced increasing collateral flow. CP in the endocardium remained severely depressed. Progressive supplementation of collateral flow early and throughout a 24 hour period of regional myocardial ischemia and the selective delivery of this flow to subepi- and mid- myocardial tissue accounts in part for the natural salvage of this tissue and the deterioration of the endocardium to necrosis. Gradients of flow and metabolism further influence these events and account for the "wave front" of cell death.

Topics: Adenosine Triphosphate; Animals; Biopsy; Collateral Circulation; Coronary Disease; Coronary Vessels; Dogs; Energy Metabolism; Female; Ligation; Male; Microspheres; Myocardial Infarction; Myocardium; Phosphocreatine; Time Factors

Exogenous phosphocreatine (PCr) and its cyclic analog, 3-phosphono-2-imino-1-methyl-4-oxoimidazolidine (PIMOI) were used as protectors of ischemic myocardium. PCr was insignificantly metabolized, whereas its analog was rapidly split, resulting in the formation of creatinine and inorganic phosphate as well as of minor amounts of PCr and creatine. Exogenous AMP and ATP accelerated PCr breakdown; in contrast, PIMOI hydrolysis slowed down in the presence of AMP. A similar inhibitory effect was observed after treatment of hearts with 2,4-dinitrofluorobenzene. These data together with those obtained for heart homogenates point to the enzymatic nature of PIMOI hydrolysis in ischemic heart. Acidic phosphatases and 5'-nucleotidases of the heart are supposed to be involved in this process.

Topics: Adenosine Monophosphate; Adenosine Triphosphate; Animals; Coronary Disease; Hydrolysis; Imidazolidines; In Vitro Techniques; Kinetics; Myocardium; Perfusion; Phosphocreatine; Rats

Provision of AMP or adenosine to heart cells during recovery from episodes of myocardial ischaemia accelerates physiological, biochemical, and structural recovery. Inhibition of adenosine loss from the tissue during ischaemia should have a similar effect. This hypothesis was tested in dog heart by infusion of adenosine and inhibitors of adenosine catabolism prior to, during, and following ischaemia. Post-ischaemic recovery of ATP and contractile function was accelerated significantly by adenosine and by inhibitors of adenosine catabolism both singly and in combination. Contractility and ATP levels during ischaemia were also increased by these inhibitors.

Topics: Adenosine; Adenosine Triphosphate; Animals; Coronary Disease; Dogs; Heart; Kinetics; Myocardial Contraction; Perfusion; Phosphocreatine

Creatine phosphate is a precursor molecule for ATP synthesis, even under ischemic conditions. We investigated its functional and metabolic effects when added to cardioplegic solution. Rat hearts were subjected to normothermic ischemia for 15 or 30 min and then freeze-clamped. During ischemia there was gradual reduction of high-energy phosphates, but the hearts with creatine phosphate supplement showed higher myocardial content of ATP and of the creatine compound. Other hearts, subjected to 20 min of ischemia, were reperfused with blood for 40 min. Creatine phosphate supplementation resulted in better left ventricular isovolumic work during spontaneous activity, but in paced activity (400 beats/min) no significant differences were seen. After reperfusion, supplemented hearts showed a tendency to higher levels of ATP and creatine phosphate. In all three groups the hearts with cardioplegic supplement had significantly increased myocardial content of pyruvate without proportional lactate increase. The results indicate that creatine phosphate may be an effective constituent in cardioplegic solution.

Topics: Animals; Coronary Disease; Heart; Heart Arrest, Induced; Heart Rate; Male; Myocardial Contraction; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains; Solutions

The effects of trimetazidine (TMZ) on ischemia-induced metabolic damage were evaluated by 31P-NMR spectroscopy in the isolated rat heart. Isolated rat hearts underwent retrograde perfusion (37 degrees C, 9.81 kPa, pH 7.4, bicarbonate buffer) and were subjected to either partial global ischemia (24 min, 0.2 ml.min-1 residual coronary flow) or total global ischemia (12 min, no flow). 31P-NMR spectra (132 accumulations, 45 degrees, 101.3 MHz) were recorded every 3 min. Changes in cardiac ATP, PC and Pi were followed, and intracellular pH was estimated from the chemical shift of Pi. Trimetazidine (TMZ) was added to the perfusion fluid at the beginning of the perfusion. The drug was used at 2 concentrations: 6.10(-7) M, with no effect upon cardiac contractility under normoxic conditions, and 6.10(-4) M, which significantly depresses cardiac work. When TMZ was used at a concentration of 6.10(-7) M, intracellular acidosis at the end of the 24 min low-flow ischemia protocol was lower than in control hearts (6.6 vs 6.0). During reperfusion, restoration of phosphorylation (as expressed by ATP/Pi ratios) was accelerated by the drug. Similar but more pronounced effects were seen following 12 min total ischemia when TMZ was used at a concentration (6.10(-4) M) which brings about a reduction in cardiac work. In this case, myocardial ATP content was also protected during ischemia. It is concluded that restoration of phosphorylation processes upon reperfusion is more rapid under the effects of trimetazidine than in control hearts. Protection of the mechanisms or structures involved in energy transfer could be due to a reduction in ischemia-induced intracellular acidosis under the effect of TMZ.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Energy Metabolism; Female; Magnetic Resonance Spectroscopy; Myocardium; Phosphates; Phosphocreatine; Phosphorylation; Piperazines; Rats; Rats, Inbred Strains; Trimetazidine

Recovery from ischaemia in heart tissue can be accelerated by addition of precursors of ATP such as AMP to the coronary circulation. Endocytosis in capillary endothelia is also stimulated by AMP; therefore endocytosis may be important in the transport of AMP from the circulation into myocytes. Alternatively, the increase in endocytotic transport itself could be responsible for accelerated recovery, irrespective of the stimulating agent. The effects of sham, AMP, cytochalasin-D (an inhibitor of endocytosis), and cytochalasin-D + AMP infusates given prior to, during, and following a 15 min ischaemic episode, were examined. AMP accelerated biochemical and functional recovery after episodes of ischaemia and stimulated endocytosis in coronary capillaries. Cytochalasin-D strongly inhibited contractility before, during, and after ischaemia, and similarly depressed ATP and creatine phosphate levels. Cytochalasin-D also strongly inhibited endocytosis and caused swelling of the capillary endothelium. When cytochalasin-D and AMP were provided together, the beneficial effects of AMP were only partially inhibited by cytochalasin-D. In fact, AMP was able to reverse most of the effects of cytochalasin-D including the inhibition of endocytosis. This suggests accelerated recovery of ischaemic myocytes requires precursors of ATP such as AMP, and the stimulation of endocytosis may abet transport of these precursors, or may be a spurious phenomenon.

Topics: Adenosine Monophosphate; Adenosine Triphosphate; Animals; Coronary Disease; Cytochalasin D; Cytochalasins; Dogs; Endocytosis; Heart; Microscopy, Electron; Myocardium; Phosphocreatine

Multidose cardioplegia has been reported to be superior to single-dose cardioplegia in protecting the heart during ischemia. However, large volumes of cardioplegic solution may be detrimental because of washout of adenine nucleotide degradation products that accumulate during ischemia, which limits recovery of adenosine triphosphate. We designed an experiment to test the effects of increasing the volume of cardioplegic solution on postischemic myocardial recovery. Four groups were studied: Group 1, initial 2 minute single dose of cardioplegic solution; Group 2, infusion of cardioplegic solution every 30 minutes for 1 minute; Group 3, infusion of cardioplegic solution every 20 minutes for 1 minute; and Group 4, infusion of cardioplegic solution every 20 minutes for 2 minutes. All groups were ischemic for 2 hours at 20 degrees C. Although washout of nucleotide degradation products during the ischemic interval increased with higher volumes of cardioplegic infusion, the total washout (infusion plus initial 5 minutes of reperfusion) was not different among all groups. The multidose groups recovered function better and had significantly higher levels of total tissue purines after 30 minutes of reperfusion. There was no difference in adenosine triphosphate levels among all groups after reperfusion. We conclude that increasing the volume of cardioplegic solution, within a clinically relevant range is not associated with increasing loss of adenine nucleotides from the cell or with impaired functional recovery of the heart.

Topics: Adenosine Triphosphate; Animals; Cold Temperature; Coronary Disease; Heart; Heart Arrest, Induced; Male; Myocardium; Perfusion; Phosphocreatine; Postoperative Period; Purines; Rats; Solutions

In this study of a canine heart model of localized reversible ischemia, a computer-based single-processing method is developed to detect and localize the epicardial projections of ischemic myocardial electrocardiograms (ECGs) during the cardiac activation, rather than the repolarization, phase. This is done by transforming ECG signals from an epicardial sensor array into the multichannel spectral domain and identifying three decision variables: (1) the frequency in hertz of the spectral peak (f0), its frequency band width 50% below the peak value (w0), and the maximum eigenvalue difference of the ECG signal's autocorrelation matrix (e0). With use of the histograms of the f0, w0, and e0 parameters of 3256 ECGs from normal and 957 from ischemic areas of myocardium obtained from 12 dogs, it was possible to predict ischemia in a new test group of nine animals from a Neyman-Pearson (NP) test in which the threshold probabilities of detecting ischemia for each decision variable are compared with those of detecting normality. Quantification of each sensor area by the NP tests revealed that, compared with the control, ECG spectra with decreased F0 and w0 and increased e0 relative to their respective thresholds had increased myocardial lactate (p less than 0.01), decreased adenosine triphosphate (ATP) (p less than 0.05), and reduced creatine phosphate (p less than 0.01). Prediction of f0 (p less than 0.0006) as a continuous variable could be obtained from the regression of the myocardial levels of ATP plus creatine phosphate, which demonstrated that this decision variable appears to directly reflect myocardial energetics. It appears that an advanced signal-processing method for ECG array data can be used to detect, localize, and quantify reversible myocardial ischemia.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Dogs; Electrocardiography; Heart Rate; Lactates; Myocardium; Phosphocreatine; Probability; Signal Processing, Computer-Assisted

The aim of this study was to investigate if dilazep is able to reduce with a direct protective action on the myocardium the deleterious effects caused by ischaemia and reperfusion. For this purpose we used an isolated rabbit heart preparation. The hearts were either perfused aerobically or made totally ischaemic for 60 min (by abolishing coronary flow) or made ischaemic for 60 min and then reperfused for 30 min. Ischaemic and reperfusion damage was measured in terms of alteration in mechanical function, lactate and CPK release, mitochondrial function and tissue content of Adenosine Triphosphate (ATP), Creatine Phosphate (CP) and calcium. Dilazep (10(-5) M) was administered in the perfusate either 20 minutes before ischaemia or only during post-ischaemic reperfusion. Ischaemia induced a decline of the endogenous stores of ATP and CP, followed by an alteration of calcium homeostasis with increase of diastolic pressure, mitochondria calcium overload and impairment of the oxidative phosphorylating capacities. On reperfusion, tissue and mitochondrial calcium increase the capacity of the mitochondria to use O2 for state III respiration was further impaired and the ATP-generating capacity reduced. Diastolic pressure increased and there was only a small recovery of active tension generation associated with massive CPK release. Administration of dilazep before ischaemia induced a negative inotropic effect which, in turn, resulted in a slowing of the rate of CP and ATP depletion during ischaemia. This protected the hearts against the ischemic, and reperfusion-induced decline in the ATP-generating and O2-utilizing capacities of the mitochondria. In addition, there was a less marked increase in tissue and mitochondrial Ca++, CPK and lactate release were reduced and the recovery of developed pressure on reperfusion was significantly increased. Administration of dilazep during reperfusion failed to modify the exacerbation of ischaemic damage caused by the readmission of coronary flow. These data suggest that dilazep benefits the ischaemic myocardium via an ATP sparing action.

Topics: Adenosine Triphosphate; Animals; Azepines; Calcium; Coronary Circulation; Coronary Disease; Dilazep; In Vitro Techniques; Male; Mitochondria, Heart; Myocardial Contraction; Myocardium; Oxygen Consumption; Phosphocreatine; Rabbits

Since abnormalities in regional myocardial function and nucleotide metabolism persist for a prolonged period after a brief coronary occlusion the temporal relation between the resolution of myocardial dysfunction and repletion of nucleotide pools in postischaemic myocardium was studied in conscious mildly sedated animals. In a second experiment 5-amino-4-imidazolecarboxamide riboside (AICAriboside) was infused in an attempt to influence myocardial function by altering the rate of adenine nucleotide synthesis. Conscious dogs mildly sedated with morphine underwent coronary occlusion for 15 min followed by reperfusion for 30 min or 12 h, at which time a myocardial sample was obtained for nucleotide analysis. Segment shortening averaged 62% of control values at 15 min of reperfusion and increased to 81% of control by 12 h of reperfusion (p less than 0.05). Adenine nucleotide content was 75(5)% of control after 30 min of reperfusion and did not change significantly over the next 12 h of reperfusion. Thus the early return of systolic function was not accompanied by a detectable increase in total adenine nucleotide content. In the second experiment a pronounced stimulation of the proximal purine nucleotide synthetic pathway occurred as evidenced by a 13-fold to 25-fold increase in inosine monophosphate content. One branch of the distal purine pathway was also stimulated as evidenced by complete repletion of guanine nucleotide pools, but the product of the other branch (adenine nucleotides) did not increase significantly. These results indicate a selective limitation of the distal adenine nucleotide synthetic pathway in postischaemic myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Aminoimidazole Carboxamide; Animals; Coronary Disease; Dogs; Heart; Hemodynamics; Myocardium; Nucleotides; Phosphocreatine; Purine Nucleotides; Ribonucleosides

Effect of diltiazem on subcellular distribution of lysosomal enzymes, high-energy phosphate metabolism and mechanical function in the ischemic heart was studied. Ischemia was induced by lowering the afterload pressure of the perfused working rat heart. The activities of cathepsin D, beta,N-acetylglucosaminidase and acid phosphatase were determined in the nonsedimentable and sedimentable fractions after centrifugation of the tissue extract to assess the subcellular distribution of lysosomal enzymes. After ischemia, decreases in the mechanical function and the tissue level of high-energy phosphates were observed. In addition, ischemia caused subcellular redistribution of lysosomal enzymes from the lysosomes to the cytoplasm. Reperfusion of the ischemic heart did not restore the mechanical function and the level of high-energy phosphates completely. Diltiazem (2.21 X 10(-6), 1.11 X 10(-5) and 2.21 X 10(-5) M) was provided for the heart 5 min before the onset of ischemia. Diltiazem preserved high-energy phosphates in the ischemic heart, and inhibited the subcellular redistribution of lysosomal enzymes being caused by ischemia, depending on its concentration. Reperfusion after ischemia with diltiazem recovered the mechanical function that had been decreased by ischemia. These results may indicate that diltiazem can protect the myocardium against ischemic damage.

Topics: Acetylglucosaminidase; Acid Phosphatase; Adenosine Triphosphate; Animals; Cathepsin D; Coronary Disease; Diltiazem; Lysosomes; Male; Myocardium; Perfusion; Phosphocreatine; Rats; Rats, Inbred Strains

To determine the characteristic appearance of phosphorus (31P) nuclear magnetic resonance spectra in acute and chronic myocardial infarction in situ, cardiac-gated depth-resolved surface coil spectroscopy (DRESS) at 1.5 T was used to monitor 31P NMR spectra from localized volumes in the left anterior canine myocardium for up to 5 days following permanent occlusion of the left anterior descending coronary artery. Coronary occlusion initially produced regional ischemia manifested as significant reductions in the phosphocreatine (PCr) to inorganic phosphate (Pi) ratios and intracellular pH (P less than 0.05, Student's t test) in endocardially displaced spectra acquired in periods as short as 50 to 150 s postocclusion. Spectra acquired subsequently revealed either (i) restoration of near-normal phosphate metabolism sometime between 10 and about 50 min postocclusion or (ii) advancing ischemic phosphate metabolism at about an hour postocclusion, and/or (iii) maintenance of depressed PCr/Pi ratios for up to 5 days postocclusion with a return of the apparent pH to near normal values between 6 and 15 h postocclusion. Postmortem examination of animals exhibiting the first type of behavior revealed the existence of coronary collateral vessels. The last type of behavior indicates that Pi remains substantially localized in damaged myocardium for days following infarction. The location and size of infarctions were determined postmortem by staining excised hearts. The smallest infarctions detected by 31P DRESS weighed 4.9 and 7.5 g. The most acidic pH measured in vivo was 5.9 +/- 0.2. Infarctions aged 1/2 day to 5 days were characterized by elevated but broad Pi resonances at 5.1 +/- 0.2 ppm relative to PCr and significantly depressed PCr/Pi ratios (P less than 0.002, Student's t test) relative to preocclusion values. Contamination of Pi resonances by phosphomonoester (PM) components is a significant problem for preocclusion Pi and pH measurements. These results should be applicable to the detection and identification of human myocardial infarction using 31P NMR and DRESS.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Dogs; Hydrogen-Ion Concentration; Magnetic Resonance Imaging; Myocardial Infarction; Myocardium; Phosphates; Phosphocreatine

We investigated whether there is a relationship between the prolonged dysfunction after myocardial ischaemia and the postischaemic phosphocreatine overshoot phenomenon. In 16 open-chest rats 3 periods of 4 minutes of oxygen deficiency were performed and basal haemodynamic variables and the myocardial oxygen demand were determined during the recovery period. At the end of the 20 minutes recovery period, left ventricular pressure, dp/dtmax, ejection fraction, and myocardial oxygen demand were completely recovered. High energy phosphate levels, however, were still altered. The sum of adeninenucleotides was decreased to 78 +/- 4% of control (mean +/- SEM, p less than 0.05). The level of phosphocreatine was markedly elevated to 162 +/- 14 (mean +/- SEM). The persistence of the phosphocreatine overshoot phenomenon, while basal function was already normalized, indicates that a reduced function and thus a reduced energy demand of the contractile apparatus are not the cause of the phosphocreatine overshoot. We found no close relationship between high energy levels and basal function or oxygen demand in myocardium after mild oxygen deficiency.

Topics: Adenine Nucleotides; Animals; Coronary Disease; Hypoxia; Kinetics; Male; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains

The effects of exogenous inosine (IN) on high-energy phosphate metabolism and function in isolated, working rabbit hearts were monitored with 31P-nuclear magnetic resonance spectroscopy. Dynamic measurements of ATP and phosphocreatine (PCr) were made along with concomitant functional recordings during normal perfusion, global ischemia (IS), and reperfusion (RE). We found that 0.1 mM IN enhanced the rate of pressure development (dP/dt) within the left ventricle by 10 +/- 5% (n = 7). Although IN levels in treated hearts were elevated during normal perfusion, no effect was observed on ATP or PCr levels. However during IS, pretreatment with IN minimized ATP loss for the first 20 min relative to untreated controls (UNT, P less than 0.05). Both IN and UNT hearts that were ischemic for only 13.5 min regained function during a 60-min RE period. However, at the end of IS, IN hearts (n = 8) displayed 88 +/- 10% of the pre-IS ATP levels, whereas UNT hearts (n = 7) retained only 60 +/- 10%. With RE, ATP in IN hearts remained elevated over that of UNT hearts for the entire 60 min. IN treatment also increased the rate of recovery of dP/dt and maintained improved function over 60 min of RE. No correlation was found between post-IS ATP levels and dP/dt values during RE in either IN or UNT hearts. These data indicate that IN was protective against ATP loss during IS and improved functional recovery on RE.

Topics: Adenosine Triphosphate; Animals; Cardiotonic Agents; Coronary Disease; Inosine; Magnetic Resonance Spectroscopy; Male; Perfusion; Phosphocreatine; Rabbits

Isolated working rat hearts which received no drug treatment had reduced ATP and creatine phosphate levels and increased lactate content during 20 min of ischemia. When subjected to 33 min of ischemia and 30 min of reperfusion, these hearts recovered low values of cardiac output (9.8 ml/min), heart rate, maximum developed pressure, pressure-rate product (72.9, 32.6, 27.5% of control, respectively), had low levels of tissue ATP, and reduced coronary flow upon reperfusion. Addition of nisoldipine (1 nM) 10 min before ischemia caused no decrease in cardiac output or heart rate, slightly decreased maximum developed pressure and pressure-rate product (93% of control), and did not reduce the degradation of ATP and creatine phosphate or the accumulation of lactate during 20 min of ischemia. When nisoldipine was included 10 min before ischemia, during ischemia (33 min) and reperfusion (30 min), however, the recovery of cardiac function and tissue ATP levels was significantly increased. This protective effect occurred when drug treated ischemic hearts were reperfused with control buffer, indicating residual effects. The beneficial effects of nisoldipine were not due to changes in afterload or preload (isolated perfused heart), collateral flow (zero flow model), energy preservation during ischemia (little contractile depression, ATP not enhanced during ischemia), or reduced lactate accumulation during ischemia. The beneficial effects were associated with increased coronary flow (31% higher than no drug) during reperfusion, indicating a reduction in the no-reflow phenomenon.

Topics: Adenosine Triphosphate; Animals; Cardiac Output; Coronary Circulation; Coronary Disease; Energy Metabolism; Heart Rate; Myocardial Contraction; Nifedipine; Nisoldipine; Phosphocreatine; Rats; Rats, Inbred Strains

An experimental study in 307 isolated rat hearts was concerned with variations in myocardial resting tension, resting membrane potential, ATP levels and myocardial heat production in conditions of cardioplegic heart arrest by an ion-balanced cardioplegic solution with and without phosphorylated metabolites (ATP, phosphocreatine, inosine-F, glucose-6-phosphate) and dephosphorylated metabolites (glucose, inosine, and inorganic phosphates). Phosphorylated metabolites, incorporated in the solution, had a marked protective effect due to the activation of substrate regulation mechanisms at different stages of ATP synthesis and facilitation of cardiomyocyte adaptation to ischemic, hypothermic and cardioplegic exposure.

Topics: Adenosine Triphosphate; Animals; Cardioplegic Solutions; Coronary Disease; Drug Synergism; Heart Arrest, Induced; In Vitro Techniques; Male; Phosphocreatine; Rats

This paper describes a method by which antianginal drugs can be evaluated in the dog heart in situ. Myocardial pH was measured continuously by a micro glass pH electrode inserted in the left ventricular endocardial layers of the dog anesthetized with pentobarbital. Occlusion of the left anterior descending coronary artery (LAD) decreased myocardial pH, and release of the LAD restored the pH. The myocardial acidosis induced by ischemia was metabolic in nature and accompanied by a decrease in the levels of adenosine triphosphate and creatine phosphate and an increase in the levels of lactate in the myocardium. Drugs were injected intravenously 30 min after incomplete (partial) occlusion ot the LAD, lasting until 60 min after drug injection. Propranolol, atenolol, and sotalol markedly attenuated the myocardial pH that had been decreased by LAD occlusion. Nitroglycerin, diltiazem, and nicorandil also attenuated the pH, but these drugs were less active in attenuating myocardial acidosis. Dipyridamole, nifedipine, and beta-2 adrenoceptor antagonists were least active in this regard. It is concluded that myocardial pH can be used as an indicator of myocardial regional ischemia and utilized for evaluation of antianginal drugs.

Topics: Acidosis; Adenosine Triphosphate; Adrenergic beta-Antagonists; Angina Pectoris; Animals; Coronary Disease; Dogs; Hydrogen-Ion Concentration; Lactates; Lactic Acid; Myocardium; Phosphocreatine; Time Factors; Vasodilator Agents

The effects of trimetazidine on ischaemia-induced metabolic damage were checked by 31 phosphore - nuclear magnetic resonance spectroscopy on the isolated rat heart. Isolated rat hearts, retrogradely perfused (37 degrees C, 9.81 kPa, pH 7.4 bicarbonate buffer) were submitted to partial global ischaemia (24 min, 0.2 ml.min-1 residual coronary flow) or total global ischaemia (12 min no flow). 31 phosphore-nuclear magnetic resonance spectra (132 i, 45 degrees, 101.3 MHz) were taken every 3 minutes. Changes in ATP, phosphocreatine and inorganic phosphore heart contents were followed, and intracellular pH was estimated from the chemical shift or inorganic phosphore. Trimetazidine was added to the perfusion fluid at the beginning of perfusion. The drug was used at two concentrations: 6.10(-7) M which has no effect on the contractility of the heart in normoxic conditions and 6.10(-4) which depresses significantly heart work. When trimetazidine was used at the concentration of 6.10(-7) M, the intracellular acidosis at the end of a 24 min low-flow ischaemia was less than in control hearts (6.6 versus 6). During reperfusion the restoration of the phosphorylation processes (as expressed by the ratio ATP/inorganic phosphore) was accelerated under the effect of the drug. Similar, but more pronounced, effects were observed in a 12 min total ischaemia when trimetazidine was given at a concentration (6.10(-4) M) which induces a reduction of cardiac work. In this case the myocardial ATP content was also protected during ischaemia. Under the effect of trimetazidine the phosphorylation processes are more rapidly restored during reperfusion than in control hearts. The protection of the mechanisms or structures involved in the energy transfers could be due to the reduction, under the effects of trimetazidine, of the intracellular acidosis induced by ischaemia.

Topics: Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Female; Hydrogen-Ion Concentration; In Vitro Techniques; Magnetic Resonance Spectroscopy; Phosphocreatine; Phosphorylation; Piperazines; Rats; Rats, Inbred Strains; Trimetazidine

Contents of high energy phosphates in the isolated perfused rat heart were followed during ischemia and reperfusion using 31P NMR spectroscopy. Application of 2-mercaptopropionylglycine resulted in significantly higher content of ATP in the reperfusion phase whereas during ischemia no differences between control and therapy hearts were found. Analysis of postischemic mitochondrial function reveals that improved ATP level is paralleled by an increased respiratory control index and a reduced ATPase activity. It is suggested that 2-mercaptopropionylglycine may cause increase of high energy phosphates during reperfusion by improving mitochondrial oxidative phosphorylation.

Topics: Adenosine Triphosphatases; Adenosine Triphosphate; Amino Acids, Sulfur; Animals; Coronary Disease; Female; Magnetic Resonance Spectroscopy; Mitochondria, Heart; Myocardium; Oxygen Consumption; Phosphocreatine; Rats; Rats, Inbred Strains; Tiopronin

The uptake of 32P-phosphocreatine by control and ischemic isolated perfused rat hearts has been studied. The rate of phosphocreatine (PCr) uptake by the hearts after 35 minutes of ischemia was two times that in control hearts at 0.5-10 mM PCr in the perfusate. At 10 mM PCr in the perfusate, this rate was 182 nmoles/min/g dry weight. The 5'-nucleotidase and phosphatase activities were found in the crude plasma membrane fraction of rat heart. The pH-dependence of these enzymes was examined. The 5'-nucleotidase activity decreased with a drop in pH from 8.0 to 6.0. The phosphatase activity in the crude plasma membrane fraction of rat heart was increased 2-fold with a decrease in pH from 8.0 to 6.0. The 5'-nucleotidase activity was inhibited by 10 mM PCr in the presence of 5 mM Mg2+. This inhibition was pH-dependent with a maximum (58%) at pH 6.0. The inhibition of phosphatase activity by PCr was independent of pH and reached 20% in the presence of 10 mM PCr. Some feasible mechanisms of the protective effect of PCr on ischemic myocardium are discussed.

Topics: 5'-Nucleotidase; Adenosine Triphosphate; Animals; Cell Membrane; Coronary Disease; Hydrogen-Ion Concentration; In Vitro Techniques; Myocardium; Nucleotidases; Phosphates; Phosphocreatine; Phosphoric Monoester Hydrolases; Phosphorylation; Rats; Rats, Inbred Strains

Absence of a Major Arrhythmogenic Role for Cyclic AMP. Journal of Molecular and Cellular Cardiology (1986) 18, 375-387. We examined the mechanism whereby beta-adrenoceptor antagonism exerts an antiarrhythmic effect in early myocardial ischaemia. Ligation of the anterior descending coronary artery in the anaesthetized open-chest pig resulted in severe transmural anteroseptal ischaemia. Blood flow in the mid-ischaemic zone 20 min after ligation was decreased to 5.7 +/- 0.7% of the preligation control value. Epicardial ST-segment deflections of 6.7 +/- 0.4 mV were recorded over this zone. A distinct phase of ventricular arrhythmias was evident about 10 to 30 min after ligation. A high incidence of ventricular fibrillation (14/16 pigs) was associated with a circumstantial increase in levels of cyclic AMP in ischaemic tissue. Twenty minute values were: 1.10 +/- 0.06, P less than 0.05 v. the non-ischaemic tissue level of 0.86 +/- 0.05 nmol/g. Propranolol 3 mg/kg IV, metoprolol 20 mg/kg IV or sotalol 10 mg/kg IV were given between 30 min prior to and 10 min after ligation. Adequate beta-adrenoceptor antagonism by each agent could be proven. Metoprolol decreased the incidence of ventricular fibrillation (2/13, P less than 0.0005 v. control group), while propranolol or sotalol did not. All three beta-antagonists decreased tissue levels of cyclic AMP prior to ligation. However, the temporary increase in ischaemic tissue after ligation could not be prevented. Furthermore, cyclic AMP in ischaemic tissue 20 min after ligation was higher in the metoprolol group than in the propranolol or sotalol group (0.94 +/- 0.04 v. 0.81 +/- 0.02 P less than 0.05, and 0.79 +/- 0.03 nmol/g P less than 0.01, respectively). Blood flow in the mid-ischaemic zone of the metoprolol group was increased to 8.6 +/- 0.6% of preligation control value (P less than 0.0001 v. control group). In contrast, blood flow in the mid-ischaemic zone of the propranolol or sotalol group was decreased. Metoprolol also reduced epicardial ST-segment deflections over the mid-ischaemic zone to 3.5 +/- 0.2 mV (P less than 0.0001 v. control group). ST-segment deflections in the propranolol group were increased. The mechanism whereby metoprolol prevented ventricular fibrillation may be explained by a decrease in the severity of ischaemia but not in terms of changes of tissue levels of cyclic AMP.

Topics: Acute Disease; Adenosine Triphosphate; Animals; Arrhythmias, Cardiac; Blood Pressure; Coronary Circulation; Coronary Disease; Cyclic AMP; Electrocardiography; Female; Heart Rate; Lactates; Male; Metoprolol; Phosphates; Phosphocreatine; Propranolol; Sotalol; Swine; Time Factors; Ventricular Fibrillation

The influence of glucose-insulin-potassium infusion in combination with a mechanical assist device (intraaortic balloon pumping, IABP) on the levels of high energy phosphates in the canine heart after coronary artery ligation was compared with the effect of a separate application of these measures to protect the acute ischaemic myocardium. The combined method normalized the tissue content of creatine phosphate in the nonischaemic tissue contrary to the application of the mechanical or pharmacological assistance alone. In the ischaemic cardiac tissue only the combination of both methods reduced the loss of creatine phosphate, ATP and the sum of adenine nucleotides. With the balloon pumping a reduction in lactate accumulation was achieved, which, however, was significantly lower than that obtained by the combination of heart protective measures: IABP plus glucose-insulin-potassium.

Topics: Adenine Nucleotides; Adenosine Triphosphate; Animals; Coronary Disease; Coronary Vessels; Dogs; Drug Therapy, Combination; Female; Glucose; Heart Ventricles; Insulin; Intra-Aortic Balloon Pumping; Kinetics; Lactates; Male; Myocardium; Phosphocreatine; Potassium; Pyruvates

The phospholipid composition of the crude plasma membrane fraction of Langendorff perfused rat hearts has been studied. The effect of phosphocreatine (PCr) and 3-phosphono-2-imino-1-methyl-4-oxoimidazolidine (PIMOI) on lysophosphoglycerides (LPG) level in this fraction isolated from hearts that were totally ischemic for 8 minutes, has been examined. The absolute and relative contents of LPG were significantly increased in ischemic hearts: the lysophosphatidylcholine content was elevated by 94% and that of lysophosphatidylethanolamine--by 77%. Accumulation of these LPG in ischemic myocardium was completely inhibited in the presence of 10 mM PCr or PIMOI in the perfusate. LPG may play a key role in the destruction of sarcolemma. Therefore, these data allow to assume that the protective effect of PCr and PIMOI on the sarcolemma of ischemic myocardium may be the result of their influence on the phospholipid metabolism in the ischemic region of the heart.

Topics: Animals; Cell Membrane; Chromatography, Thin Layer; Coronary Disease; Depression, Chemical; Glycerophosphates; Membrane Lipids; Myocardium; Phosphocreatine; Phospholipids; Rats; Rats, Inbred Strains

Phosphorus-31 nuclear magnetic resonance spectroscopy (31P NMR) was used to assess the temporal changes of high-energy phosphate metabolites in the region of acute myocardial ischemia of open-chest cats. Eight anesthetized cats were studied following ligation of the left anterior descending coronary artery. Creatine phosphate showed a 79 +/- 16% (mean +/- SD) reduction by 4 min after the onset of ischemia. Prominent qualitative reductions of the spectral peak of creatine phosphate occurred by 40 s after ischemia. Adenosine triphosphate measured under the beta spectral peak (beta-ATP) decreased 37 +/- 9% by 20-25 min after ligation of the left anterior descending coronary artery. These reductions developed more slowly and were of smaller magnitude than those of creatine phosphate. Intracellular pH decreased from 7.39 +/- 0.07 to 7.13 +/- 0.09 units by 40 s after ischemia. By 30 min, pH decreased to 6.07 +/- 0.40 units. The study shows, therefore, the temporal changes of high-energy phosphate metabolites during ischemia in localized regions of the myocardium of open-chest animals.

Topics: Adenosine Triphosphate; Animals; Cats; Coronary Disease; Female; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Male; Myocardium; Phosphocreatine; Phosphorus; Spectrum Analysis; Time Factors

Changes in the content of lysophosphoglycerides in a crude plasmalemmal fraction of canine heart during short-term ischemia (occlusion of the left descending coronary artery for 8 min) have been studied in the presence and in the absence of phosphocreatine and phosphocreatinine. In the control experiments without PCr or PCr-nine ischemia caused significant elevation of the content of LPG: that of lysophosphatidylcholine was increased by 83% and that of lysophosphatidylethanolamine by 168%. Intravenous administration of PCr and PCr-nine in doses of 300 mg/kg completely prevented accumulation of LPG in the ischemic zone. Because of the well-known arrhythmogenic properties of LPG, the inhibitory effect of PCr and PCr-nine on the elevation of their concentration in the ischemic zone may be closely related to the antiarrhythmic action of PCr and PCr-nine in acute myocardial ischemia.

Topics: Animals; Chromatography, Thin Layer; Coronary Disease; Dogs; Female; Heart; Kinetics; Male; Myocardium; Phosphocreatine; Phospholipids

Myocardial exogenous substrate preference was studied under conditions of increased plasma lactate concentration before and after a severe (halving of tissue ATP concentration, sixfold increase in tissue lactate concentration) but reversible (less than 1% necrosis on reperfusion) global ischaemic stress produced by continuous hypothermic electromechanical arrest of the heart of four hours' duration by aortic cross clamping and multidose potassium cardioplegia. Fatty acid oxidation was studied using 1-14C-palmitate under steady state conditions and under similar isovolumic fixed pressure conditions with the heart at a constant rate using a left ventricular intracavitary balloon. Exogenous free fatty acid oxidation during the pre-ischaemic period with an increased lactate concentration (3.9-5.8 mmol . litre-1) was 0.62(0.21) mumol . min-1 X 100 g-1 (mean (SEM)). This represented a mean of 32% of the total carbon dioxide produced in contrast to a post-ischaemia free fatty oxidation rate of 2.67(0.87) mumol . min-1 X 100 g-1, in the presence of even further increased plasma lactate concentrations (8.47-11.17 mmol . litre-1), representing a mean of 82% of the total carbon dioxide output. These data suggest that the substrate preference of the myocardium, under conditions of increased plasma lactate concentration, shifts to greater oxidation of exogenous free fatty acids after ischaemic stress.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Disease Models, Animal; Dogs; Fatty Acids, Nonesterified; Glycogen; Heart; Lactates; Myocardial Contraction; Myocardium; Oxygen; Phosphocreatine

Topics: Adenosine Triphosphate; Animals; Calcium; Cell Membrane Permeability; Cell Survival; Coronary Circulation; Coronary Disease; Glutathione; Magnesium; Mitochondria, Heart; Myocardium; Oxygen; Perfusion; Phosphocreatine; Rabbits; Superoxide Dismutase

Topics: Adenosine Triphosphate; Animals; Calcium; Coronary Circulation; Coronary Disease; Energy Metabolism; Homeostasis; Humans; Hypoxia; Myocardium; Oxygen; Phosphocreatine; Time Factors

The effect of diltiazem on post-ischemic metabolic and functional recovery was investigated in regionally ischemic dog hearts. The duration of ischemia was 60 min, followed by 60 min of reperfusion. Diltiazem (bolus injection of 0.1 mg X kg-1 body weight prior to ischemia, followed by a continuous infusion of 0.1 mg X kg-1 X h-1) had no effect on residual coronary flow in the centre of the ischemic area, but blunted the reactive hyperemia response after restoration of flow. The drug partially prevented the depletion of ATP and glycogen in the severely underperfused subendocardial layers, i.e. when residual flow was below 0.1 ml X min-1 X g-1. Reduction of the content of these substances in the subepicardial layers was moderate and not influenced by diltiazem. Segment shortening in the subepicardial layers disappeared whereas segment lengthening was observed in the subendocardial layers during the ischemic period. Diltiazem did not prevent the loss of contractile function. Despite an initial restoration of contractile function within 10 min after reperfusion, no significant beneficial effect of diltiazem treatment on mechanical function of the reperfused area was present thereafter.

Topics: Adenosine Triphosphate; Animals; Benzazepines; Cardiac Output; Coronary Circulation; Coronary Disease; Diltiazem; Dogs; Female; Glycogen; Heart; Male; Myocardial Contraction; Myocardium; Phosphocreatine; Time Factors

Topics: Aerobiosis; Animals; Blood Pressure; Brain; Coronary Disease; Energy Metabolism; Humans; Hydrogen-Ion Concentration; Liver; Magnetic Resonance Spectroscopy; Magnetics; Muscles; Myocardium; Phosphocreatine; Phosphorus; Physical Exertion

The contribution of long-chain acyl carnitine to increase enzyme release during ischemia was investigated both in normal and diabetic rat hearts. 2-Tetradecylglycidic acid (TDGA) was used to inhibit acyl carnitine formation. Isolated working-heart preparations were perfused with glucose (11 mM) and palmitate (0.1 mM) in control and mild ischemic conditions. Ischemia induced lactate dehydrogenase (LDH) release from both normal and diabetic hearts, but the release was higher from the diabetics over a 15-min ischemic period. The ischemia-induced tissue accumulation of long-chain acyl carnitine also was greater in diabetic hearts compared with normal hearts. When TDGA was provided in the perfusate 10 min before the addition of palmitate, levels of acyl carnitine were significantly reduced (by approximately 80%) in the ischemic tissue of both groups of hearts. Similarly, LDH release from ischemic hearts was markedly decreased in the presence of TDGA. A positive correlation was shown between LDH release over the ischemic period and the tissue levels of acyl carnitine at the end of ischemia. Significant improvement in mechanical function with TDGA was only observed in ischemic diabetic hearts. There was absolutely no difference in high-energy compounds under a given perfusion condition, either with or without TDGA, between normal and diabetic hearts. It is concluded that lessening the accumulation of fatty acid intermediates, such as acyl carnitine, may be important to prevent or to limit the loss of sarcolemmal integrity under ischemic conditions, especially in diabetic hearts.

Topics: Acetylcarnitine; Adenosine Triphosphate; Animals; Carnitine; Coronary Disease; Diabetes Mellitus, Experimental; Epoxy Compounds; Ethers, Cyclic; Fatty Acids; L-Lactate Dehydrogenase; Male; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains

This study tests the hypothesis that the oxygen radical scavenger coenzyme Q10 can be given both intravenously and in the cardioplegic solution and can improve muscle salvage following surgical revascularization. Pilot studies were carried out in dogs undergoing 40 minutes of coronary artery ligation with reperfusion with normal blood, with the heart in the beating, working state. Intravenous infusions of coenzyme Q10 (10 mg/kg) 5 minutes before reperfusion resulted in improved recovery of creatine phosphate, adenosine triphosphate, total adenine nucleotide, and myocardial function reverse estimated by postextrasystolic potentiation, in comparison with the degree of recovery in untreated dogs. Experimental studies were done on 27 dogs undergoing 2 hours of left anterior descending coronary artery occlusion and subsequent reperfusion with and without total vented bypass. Thirteen dogs received intravenous coenzyme Q10 10 minutes before extracorporeal circulation, six received substrate-enriched blood cardioplegic solution with added coenzyme Q10, and six received normal blood reperfusate. Six others had cardioplegic reperfusion without coenzyme Q10. The systolic bulging that occurred during ischemia (ultrasonic crystals) persisted after reperfusion with normal blood (-25% systolic shortening, p less than 0.05), and 44% transmural triphenyltetrazolium chloride nonstaining occurred in the area at risk. Conversely, hearts receiving substrate-enriched blood cardioplegic solution recovered 37% contractility (p less than 0.05), with the least, and only, subendocardial triphenyltetrazolium chloride nonstaining (25% of area at risk) occurring with intravenous coenzyme Q10 before bypass and coenzyme Q10 supplementation of the cardioplegic solution. Intravenous coenzyme Q10, given just before reperfusion (possibly in transit to the operating room), enhances the role of substrate-enriched blood cardioplegic solution (especially when added to the cardioplegic solution) in salvaging ischemic myocardium and allowing immediate functional recovery.

Topics: Adenosine Triphosphate; Animals; Coenzymes; Coronary Circulation; Coronary Disease; Dogs; Heart Arrest, Induced; Infusions, Parenteral; Myocardial Revascularization; Phosphocreatine; Ubiquinone

This study compares blood versus crystalloid cardioplegia in restoring contractile function, and high-energy phosphate and tissue water content in a myocardial segment after 1 hour of coronary artery occlusion. Anesthetized dogs underwent instrumentation with the chest open to measure left ventricular and aortic pressures, and systolic shortening in the myocardium perfused by the left anterior descending coronary artery (LAD) was measured with ultrasonic crystals. In 21 dogs, the LAD was occluded for an hour, thereby replacing systolic shortening with passive lengthening averaging -28.7 +/- 6.2% of control shortening in both groups. The dogs were then placed on total bypass, and arrest was achieved with multidose crystalloid (N = 10) or blood cardioplegia (N = 11). The ligatures were released just prior to the second infusion of cardioplegic solution. Postischemic subendocardial levels of adenosine triphosphate were comparably depleted with crystalloid and blood cardioplegia (55.2% and 44.0%, respectively, of control). Subendocardial increases in water content were similar for crystalloid (3.62%) and blood (3.16%) cardioplegia. Recovery of segmental shortening was significantly greater with blood than crystalloid cardioplegia (31.5 +/- 8.2% versus 4.9 +/- 6.6% of control, respectively). We conclude that the composition and the delivery of blood cardioplegia used in this study restore greater postischemic function than crystalloid cardioplegia in acute evolving myocardial infarction.

Topics: Adenosine Triphosphate; Animals; Body Water; Coronary Circulation; Coronary Disease; Dogs; Evaluation Studies as Topic; Heart Arrest, Induced; Myocardial Contraction; Myocardium; Necrosis; Phosphocreatine; Postoperative Period; Potassium; Potassium Compounds

Reocclusion after successful coronary reperfusion occurs in 15 to 35% of patients receiving thrombolytic therapy for acute myocardial infarction. The present study was designed to simulate the clinical situation of reocclusion and determine whether verapamil might be effective in reducing myocardial necrosis and preserving high energy phosphates in this setting. Pentobarbital-anesthetized, open chest dogs underwent occlusion of the left anterior descending coronary artery for 2 hours followed by 1 hour of reperfusion and a further 4 hours of coronary artery occlusion. Treatment with verapamil (intravenous bolus dose of 0.2 mg/kg body weight followed by infusion of 0.56 +/- 0.14 mg/kg per h) was begun 1 hour after occlusion and infusion was continued for the remainder of the experiment. The dose of verapamil was adjusted to lower mean arterial pressure to approximately 90 mm Hg. The area at risk was determined by intraatrial injection of monastral blue dye and the area of necrosis was assessed by triphenyltetrazolium chloride staining. In vivo myocardial needle biopsy for determination of adenosine triphosphate and creatine phosphate was performed at the end of the experiment. The area of the left ventricle at risk was similar in both groups (control [n = 8], 20.2 +/- 1.6% versus verapamil-treated [n = 9], 23.1 +/- 2.9%; p = NS). The area of necrosis expressed as a percent of the area at risk was reduced in the verapamil-treated group compared with the control group (43.3 +/- 5.0% versus 63.1 +/- 6.8%, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Coronary Circulation; Coronary Disease; Dogs; Female; Male; Myocardium; Necrosis; Phosphocreatine; Recurrence; Verapamil

The difference between normotensive rats (WKY) and spontaneously hypertensive rats (SHR) in functional and metabolic responses to ischemia was studied. Systolic arterial blood pressure of SHR (171.2 +/- 2.9 mmHg) was significantly higher than that of WKY (135.3 +/- 1.2 mmHg), and the left ventricular mass of SHR was larger than that of WKY. Hearts isolated from either WKY or SHR were perfused by the working heart technique. Ischemia was induced by lowering the afterload pressure of the working heart. Ischemia produced cardiac arrest, and decreased the tissue levels of adenosine triphosphate and creatine phosphate in both WKY and SHR. Recovery of mechanical function of the heart during reperfusion following ischemia in SHR was better than that in WKY, while recovery of the high-energy phosphates level in SHR was less prominent than in WKY. It is postulated that hypertension has a deleterious effect on myocardial energy metabolism in ischemic heart, even when cardiac mechanical function is maintained.

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Coronary Circulation; Coronary Disease; Lactates; Phosphocreatine; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Species Specificity

The effect of exogenous phosphocreatine on ischemic myocardium was studied in experimental infarction in rabbits and in total ischemia of pig heart tissue (in vitro). It is shown that single dose administration of phosphocreatine is followed by its rapid clearance from blood plasma (with a half lifetime of 4-6 min), but constantly high plasma concentration of phosphocreatine can be maintained by its intravenous infusion. When administered by this method into rabbits during experimental myocardial infarction, phosphocreatine reduces by 40% the size of the necrotic zone. Morphological electron microscopic studies using a lanthanum tracer method showed significant protection of the sarcolemma of cardiomyocytes in the perinecrotic zone by phosphocreatine. In vitro studies on the model of total ischemia also showed significant protection of cardiac sarcolemma from irreversible ischemic injury and reduction in the rate of high-energy phosphate depletion in the presence of phosphocreatine in the extracellular space. Additionally, it is demonstrated that creatine kinase released during myocardial infarction into the blood flow and exogenous phosphocreatine administered intravenously may significantly inhibit platelet aggregation by rapid removal of ADP, and thus potentially improve microcirculation during myocardial infarction.

Topics: Adult; Animals; Coronary Disease; Creatine Kinase; Dogs; Humans; Kinetics; Microscopy, Electron; Middle Aged; Myocardial Infarction; Myocardium; Phosphocreatine; Platelet Aggregation; Rabbits; Sarcolemma

The effects of L-propionylcarnitine on the recovery of cardiac contractile performance after global ischaemia and reperfusion were studied in isolated perfused rat hearts. The addition of either 5.5 or 11 mmol X litre-1 L-propionylcarnitine significantly improved the recovery of cardiac output, left ventricular pressure, and dP/dt after 90 min of ischaemia and 15 min of reperfusion. Myocardial adenosine triphosphate and creatine phosphate concentrations were significantly higher in the L-propionylcarnitine treated hearts than in controls, but the concentrations of long chain acyl carnitine and coenzyme A were unaffected. The protecting effects of L-propionylcarnitine were compared with those of L-carnitine and L-acetylcarnitine. A 11 mmol X litre-1 dose of L-propionylcarnitine and L-acetylcarnitine significantly improved the recovery of cardiac output after 90 min of ischaemia and 15 min of reperfusion, but L-carnitine did not. L-Propionylcarnitine was the most protective agent. The effects of these derivatives on L-3H-carnitine transport and 14C-palmitate oxidation were also measured. All of these derivatives competitively inhibited L-3H-carnitine transport in isolated cardiac myocytes, but L-propionylcarnitine was the most potent. Carnitine and L-propionylcarnitine stimulated palmitate oxidation in the homogenate, whereas L-acetylcarnitine inhibited it. In myocytes only L-propionylcarnitine affected palmitate oxidation. These data show that L-propionylcarnitine protects the ischaemic myocardium. Its protection is greater than that for L-carnitine or L-acetylcarnitine, and the difference in effectiveness may relate to the rate of transport into the cells and the effects on fatty acid utilisation.

Topics: Acetylcarnitine; Adenosine Triphosphate; Animals; Blood Pressure; Cardiac Output; Carnitine; Coronary Disease; Fatty Acids; Male; Myocardial Contraction; Myocardium; Oxidation-Reduction; Palmitic Acid; Palmitic Acids; Phosphocreatine; Rats; Rats, Inbred Strains

Catecholamines stimulate adenosine triphosphate consumption and glycogenolysis in isolated hearts. In ischaemic myocardium a protective effect of beta adrenergic blockade may therefore arise from reduced adenosine triphosphate consumption or attenuation of acidosis. To characterise the biochemical mechanism of this protective effect phosphorus metabolite concentrations and intracellular pH were measured in an ischaemic region of the rabbit heart in vivo using 31P-nuclear magnetic resonance spectroscopy. After occlusion of the left anterior descending coronary artery there was a rapid decrease in intracellular phosphocreatine concentrations, and intracellular adenosine triphosphate concentrations decreased at a rate of approximately 0.5 mumol X g-1 dry weight X min-1. Intracellular pH decreased approximately linearly to a final pH of about 5.8. In the ischaemic myocardium of the animals treated with propranolol the intracellular concentrations of adenosine triphosphate were higher and those of phosphocreatine lower and the pH was the same compared with control after 30 minutes of ischaemia. Thus any protective effect of propranolol in vivo is not associated with attenuation of intracellular acidosis in this preparation.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Male; Metabolism; Myocardium; Phosphates; Phosphocreatine; Propranolol; Rabbits

A detailed analysis was made of the changes in canine myocardium, with time of occlusion, in several important metabolites such as creatine phosphate and adenosine triphosphate (luminometry), inorganic phosphate (spectrophotometry), and most of the purines and nicotinamide adenine dinucleotide (high performance liquid chromatography). Within 1 min there was a significant reduction in creatine phosphate and a significant increase in inorganic phosphate, adenosine diphosphate, and adenosine monophosphate. A decrease in adenosine triphosphate became apparent after 4 min, concomitant with a progressive rise in the nucleosides, which reached almost 50% of the total purines after 64 min of occlusion. The formation of hypoxanthine was detectable in 50% only of all animals, suggesting a lack of active nucleoside phosphorylase in the others. Nicotinamide adenine dinucleotide, although decreasing slightly, was by far the most constant of all variables measured during at least 30 min of ischaemia. Therefore, this component is suggested to be a useful internal standard, thus minimising analytical and biological variations. Mioflazine, a potent nucleoside transport inhibitor (I50 3 X 10(-8) mol X litre-1), when given orally at 2.5 mg X kg-1, did not affect any of the changes with the exception of the nucleosides, where the drug completely inverts the adenosine to inosine ratio. The contribution of adenosine to the total nucleosides changed from 20% in the controls to 80% with treatment during at least 16 min of occlusion, there being no overlap between the groups. It is concluded therefore that adenosine is not deaminated in the cell where it is produced. It is not yet clear how this notable effect of mioflazine could be linked to its remarkable protective effect against ischaemia.

Topics: Animals; Coronary Disease; Dogs; Heart; Myocardium; Nucleosides; Phosphates; Phosphocreatine; Piperazines; Purines; Time Factors

An isolated perfused working rat heart preparation was used to assess the effect of including creatine phosphate (10 mmol/l) in the perfusion fluid of hearts subjected to aerobic perfusion (20 min), regional ischaemia (15 min) and reperfusion (2 min). Creatine phosphate had no detectable effect upon pre-ischaemic, ischaemic or post-ischaemic contractile function, it also had no statistically significant effect upon myocardial tissue ATP content. However, creatine phosphate was found to afford striking protection against reperfusion-induced arrhythmias. The incidence of ventricular fibrillation was reduced from over 80% (13/16) in the control group to 10% in the creatine phosphate-treated group (P less than 0.001). Possible mechanisms underlying the anti-arrhythmic effects of creatine phosphate were investigated using isolated rat papillary muscles superfused with or without added creatine phosphate (10 mmol/l). During aerobic superfusion at 37 degrees C creatine phosphate did not cause any statistically significant changes in contractile (developed tension) or electrophysiological (dV/dtmax and action potential duration) indices. Creatine phosphate did however influence the extent to which hypoxia (10 min) and reoxygenation (10 min) altered tension and electrophysiological characteristics. It accelerated the hypoxia-induced decline in developed tension and also the reoxygenation-induced recovery of developed tension. Relatively small changes in dV/dtmax and action potential duration were observed during hypoxia and these rapidly normalized during reoxygenation. In general creatine phosphate acted to exacerbate any changes during hypoxia and accelerate the recovery during reoxygenation. While some of the electrophysiological changes observed would indicate an anti-arrhythmic effect, they were relatively small and perhaps insufficient to explain fully the potent anti-arrhythmic properties of creatine phosphate.

Topics: Adenosine Triphosphate; Animals; Arrhythmias, Cardiac; Coronary Disease; In Vitro Techniques; Male; Myocardial Contraction; Myocardium; Oxygen Consumption; Perfusion; Phosphocreatine; Rats; Rats, Inbred Strains

Topics: Animals; Blood Pressure; Calcium; Coronary Disease; Myocardium; Phosphocreatine; Phospholipids; Rats; Rats, Inbred Strains

This study was designed to compare the effects of the Ca2+ slow channel blocking agents verapamil (2 X 10(-6) M), diltiazem (7.5 X 10(-7) M), and buffer containing reduced Ca2+ content (0.95 mM) on myocardial ischemic injury. These treatments were equiactive, reducing cardiac function to 20% of the control value, and fully reversible in nonischemic, isolated, working rat hearts. Hearts which were reperfused (30 min) following 27 min of global ischemia recovered 17% of control cardiac function and had a markedly reduced ATP and creatine phosphate content and ATP/ADP ratio compared to nonischemic hearts. When verapamil, diltiazem, nifedipine, or low Ca2+ treatments were given before and during ischemia, equal improvement in cardiac function was observed upon reperfusion, and tissue ATP levels, creatine phosphate levels, and ATP/ADP ratio were significantly higher than in hearts which did not receive the treatments or which received the drug vehicle. Large increases in recovery of contractile function were observed with a partial preservation of ATP reserves. These treatments, which were equiactive in nonischemic hearts, provided equivalent preservation of cardiac function, ATP, and creatine phosphate in the reperfused ischemic hearts. When the ischemic period was increased to 33 min and the effective concentrations reduced to depress cardiac function to 40% of the control value (4.5 X 10(-7) M verapamil, 2.5 X 10(-6) M diltiazem, 3 X 10(-7) M Nifedipine, 1.25 mM Ca2+), equal improvement in cardiac function was again observed. Thus, major differences among these Ca2+ slow channel blockers or low Ca2+ treatment were not detected in this experimental system.

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Animals; Benzazepines; Blood Pressure; Buffers; Calcium; Coronary Disease; Diltiazem; Heart Rate; Myocardial Contraction; Nifedipine; Perfusion; Phosphocreatine; Rats; Verapamil

Myocardial metabolism in live guinea pigs was investigated by 13C and 31P nuclear magnetic resonance (NMR) at 20.18 and 32.5 MHz, respectively. 13C NMR studies allowed monitoring of myocardial glycogen synthesis during intravenous infusion of D-[1-13C]glucose and insulin. Anoxia resulted in degradation of the labeled glycogen within 6 min and appearance of 13C label in lactic acid. Infusion of sodium [2-13C]acetate resulted in incorporation of label into the C-4, C-2, and C-3 positions of glutamate, reflecting "scrambling" of the label expected from tricarboxylic-acid-cycle activity. 31P NMR spectra of heart in live guinea pigs were obtained continuously in 20.5-sec time blocks during 3 min of anoxia, during subsequent reoxygenation, and, in separate animals, during terminal anoxia. Reversible anoxia resulted in rapid degradation of phosphocreatine (t1/2 = 54.5 +/- 2.5 sec), which recovered fully during reoxygenation. Heart inorganic phosphate increased during anoxia and returned to basal levels after oxygen was restored. During 3 min of anoxia, no significant changes in ATP levels or pH were detected.

Topics: Adenosine Triphosphate; Animals; Carbon Isotopes; Coronary Disease; Energy Metabolism; Female; Glucose Solution, Hypertonic; Glutamates; Glutamic Acid; Glycogen; Guinea Pigs; Heart Arrest; Hydrogen-Ion Concentration; Insulin; Lactates; Lactic Acid; Magnetic Resonance Spectroscopy; Myocardium; Phosphates; Phosphocreatine; Phosphorus Isotopes

Experiments were undertaken to establish whether prazosin prevents isolated hearts from gaining excess Ca2+ during post-ischaemic reperfusion, to determine whether this effect is dose-dependent, if it is accompanied by a change in the energy-rich phosphate reserves, and whether prazosin is effective when added only upon reperfusion. Isolated, spontaneously beating rat hearts were used. The ischaemic episodes ranged from 15 to 60 min, and prazosin (0.01 to 10 micro mol/1) was added both before inducing ischaemia and upon reperfusion. When 0.01 to 1 micro mol/1 prazosin was present before and after the ischaemic episode the reperfusion-induced gain in Ca2+ was attenuated, but not abolished. Pretreatment with 0.01 to 1 micro mol/1 prazosin slowed the ischaemic-induced rise in resting tension, enhanced mechanical recovery after 30 but not 60 min ischaemia, and exerted a dose-dependent slowing effect on the ischaemia-induced depletion of ATP and CP, with 1 micro mol/1 being the optimal dose. Adding 0.01 to 1 micro mol/1 prazosin at the time of reperfusion neither prevented excess Ca2+ accumulation upon reperfusion nor did it exert an energy-sparing effect. 5 to 10 micro mol/1 prazosin did not attenuate the reperfusion-induced gain in Ca2+, irrespective of whether it was added before or only at the time of reperfusion. These results show that the dose-response curve for the inhibitory effect of prazosin on Ca2+ overload is complex, and that adding prazosin coincident with the reperfusion of isolated ischaemic hearts does not attenuate Ca2+ gain.

Topics: Adenosine Triphosphate; Animals; Calcium; Coronary Disease; Diltiazem; Male; Myocardial Contraction; Myocardium; Phosphocreatine; Prazosin; Quinazolines; Rats; Receptors, Adrenergic, alpha

Topics: Adenosine Triphosphate; Animals; Calcium; Coronary Circulation; Coronary Disease; Fatty Acids; Humans; Hypoxia; Mitochondria, Heart; Myocardium; Oxygen; Phosphocreatine

Phosphorus (31P) NMR spectra showing the relative concentrations of phosphocreatine, ATP, and Pi were recorded noninvasively from localized regions in the left ventricles of dog hearts in situ by using depth-resolved surface-coil spectroscopy at 1.5 T. Proton (1H) NMR surface-coil imaging was used to position 31P NMR coils and to determine the location of depth-resolved volumes immediately prior to 31P examination. Occlusion of the left anterior descending coronary artery produced regional ischemia detected as changes in the ratios of phosphocreatine, ATP, and Pi and by changes in the pH measured from the spectra. Spectral changes were not typically observed in regions adjacent to ischemic myocardium. Reperfusion produced some recovery, and ventricular fibrillation resulted in deterioration in high-energy metabolites. The location and size of ischemic tissue was measured by single-photon-emission computed tomography (SPECT) and gamma-ray counting or by staining excised hearts. The technique should permit the long-term noninvasive monitoring of the metabolic response of the heart to pathologic processes and allow assessment of interventions.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Dogs; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Phosphates; Phosphocreatine

Enflurane is a direct myocardial depressant and may act as a myocardial protective agent during ischemia. The authors studied the effects of enflurane on myocardial high-energy phosphates and tolerance to ischemia in the normothermic, isolated rat heart. After isolation and perfusion with Krebs-Henseleit buffer, the hearts were perfused with either buffer (control) or buffer gassed with 2% enflurane for 10 minutes. Thereafter, hearts were made globally ischemic and elapsed times to initiation of ischemic contracture (IC) were determined. ATP and creatine phosphate (CP) were measured at the conclusion of control and enflurane administration and at IC. Ten hearts per group were reperfused with buffer following IC for 20 min; peak pressure and ATP and CP were determined. Administration of 2% enflurane significantly decreased peak pressure by 20% but did not alter baseline high-energy phosphate levels nor did it prolong time to IC. However, enflurane-treated hearts exhibited significantly greater (P less than 0.01) recovery of function as defined by per cent return of peak pressure (67% +/- 3%) when compared with those hearts not treated with enflurane preischemically (44% +/- 5%). Also, enflurane-treated hearts had significantly higher (P less than 0.01) ATP levels at the conclusion of reperfusion than hearts not perfused with enflurane (12.2 +/- .8 mumol/g dry weight vs. 9.0 +/- 0.8 mumol/g dry weight). These findings suggest that enflurane administered prior to an ischemic interval enhances postischemic myocardial recovery.

Topics: Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Enflurane; Heart; Male; Myocardial Contraction; Myocardium; Oxygen Consumption; Phosphocreatine; Rats; Rats, Inbred Strains

To evaluate effects of coenzyme Q10 added to a potassium cardioplegic solution for myocardial protection, 17 mongrel dogs underwent 60 minutes of ischemic cardiac arrest under cardiopulmonary bypass. Cardiac arrest was induced by infusing the cardioplegic solution into the aortic root every 20 minutes. Experimental animals were divided into three groups according to the cardioplegic solution used. In Group 1, we used our clinical potassium cardioplegic solution (K+, 22.31 mEq/L); in Group 2, potassium cardioplegic solution with coenzyme Q10 added (coenzyme Q10, 30 mg/500 ml of solution); and in Group 3, cardioplegic solution with coenzyme Q10 solvent. Exogenous coenzyme Q10 in the cardioplegic solution provided significantly high myocardial stores of adenosine triphosphate and creatine phosphate and a low level of lactate during induced ischemia and reperfusion. Furthermore, percent recovery of the aortic flow in Group 2 was significantly higher than that in the other two groups. Ultrastructures of the ischemic myocardium in Group 2 were better preserved than those in Group 1. Addition of coenzyme Q10 to potassium cardioplegia resulted in improved myocardial oxygen utilization and accelerated recovery of myocardial energy metabolism after reestablishment of circulation.

Topics: Adenosine Triphosphate; Animals; Cardiopulmonary Bypass; Coenzymes; Coronary Disease; Creatine Kinase; Dogs; Female; Heart Arrest, Induced; Hemodynamics; Isoenzymes; Lactates; Male; Myocardium; Oxygen; Phosphocreatine; Potassium; Potassium Compounds; Ubiquinone

The protective effects of cardioplegic solutions (CS) containing creatine phosphate (CP) were studied in a rat heart model of cardiopulmonary bypass and ischemic cardiac arrest. Isolated rat hearts were subjected to a 3-minute coronary infusion with CS containing CP in normothermic (37 degrees C) and hypothermic (4-6 degrees C) regimes. In the normothermia group, the postischemic functional recovery was 70-75% of the preischemic control value, while the cellular ATP and CP content was reduced but insignificantly. By contrast, in the hypothermia group, the postischemic functional recovery was markedly depressed, with the tissue high-energy phosphate content being appreciably lowered. The data obtained confirm high efficacy of CP-containing cardioplegic solutions administered under normothermia conditions.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Drug Evaluation, Preclinical; Heart Arrest, Induced; Hypothermia, Induced; In Vitro Techniques; Male; Phosphocreatine; Rats; Rats, Inbred Strains; Solutions

The purpose of this study was (1) to monitor myocardial high-energy phosphate content and recovery of left ventricular (LV) contractile function following normothermic graded cardiac ischemia and single-dose hypothermic potassium cardioplegia, and (2) to assess the temporal limits of LV functional recovery during single-dose cardioplegia maintained at 17 degrees C. Rabbit hearts (30) were perfused, equipped with an LV balloon, paced at 240 beats/min, and placed in a nuclear magnetic resonance (NMR) magnet. Hearts underwent either graded, global normothermic ischemia or potassium cardioplegia arrest maintained at 17 degrees C for 1 hr. Myocardial high-energy phosphate level, LV contractility, and temperature were monitored continuously. Phosphocreatine (PCr) fell to 10 +/- 2, 2 +/- 1, and 0% of control and ATP to 70 +/- 3, 19 +/- 7, and 0% of control at 10, 40, and 60 min of 37 degrees C ischemia. After 1 hr of reperfusion, regression analysis of final developed pressure (DP) on end ischemic ATP (EIATP) content revealed: DP = 1.02 EIATP + 18 (r = 0.95). Following single-dose cardioplegia, maintained at 17 degrees C, PCr fell to 16 +/- 3% of control at 60 min while ATP fell only to 92 +/- 5% control. With reperfusion, recovery of DP was 100%. It was concluded that (1) PCr serves as an energy buffer for ATP, (2) EIATP predicts recovery of LV function, (3) single-dose cardioplegia maintained at 17 degrees C provides complete myocardial preservation for up to 60 min.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Evaluation Studies as Topic; Heart; Heart Ventricles; Hydrogen-Ion Concentration; Intracellular Fluid; Magnetic Resonance Spectroscopy; Male; Monitoring, Physiologic; Myocardium; Organ Preservation; Phosphates; Phosphocreatine; Phosphorus; Rabbits

The purpose of this study was to determine noninvasively some critical level of high-energy phosphate stores that relates to the recovery of ventricular contractile function after graded cardiac ischemia. Rabbit hearts (n = 30) were equipped with an intraventricular balloon to monitor developed pressure and +/- dp/dt and placed in a nuclear magnetic resonance magnet (Bruker, 4.7 Tesla). Each heart underwent 10, 20, 40, or 60 minutes of global ischemia followed by 1 hour of reperfusion. The pH as determined by nuclear magnetic resonance dropped from 7.14 +/- 0.04 to 7.07 +/- 0.07 (p less than 0.02) at 1 minute and to 6.19 +/- 0.08 at 30 minutes of ischemia; pH ceased to fall thereafter. Phosphocreatine was depleted to 10% +/- 7% of its preischemic control in 10 minutes. Adenosine triphosphate (ATP) concentrations were 71% +/- 14% and 1% +/- 2% at 10 and 60 minutes. Regression analysis of recovered developed pressure on end-ischemic ATP (EIATP) revealed: developed pressure = 0.93 (EIATP) + 23 (r2 = 0.99). We conclude that: anaerobic metabolism as evidenced by a fall in pH appears to be active for 30 minutes after normothermic ischemia and then ceases; phosphocreatine buffers the fall in ATP during early ischemia; there is a tight correlation between EIATP and recovery of left ventricular contractile function with a threshold content of approximately 80% below which recovery of function will not be complete.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Energy Metabolism; Heart Ventricles; Hydrogen-Ion Concentration; In Vitro Techniques; Magnetic Resonance Spectroscopy; Myocardial Contraction; Myocardium; Perfusion; Phosphates; Phosphocreatine; Prognosis; Rabbits; Time Factors

Cardiac energy metabolism is one of the earliest metabolic activities affected when either anoxia or ischemia are induced, as evidenced by the rapid decline of the tissue high-energy phosphate content of creatinephosphate (CrP) and ATP. Several reports deal with the spatial inhomogeneity of these changes and it is generally found, that the subendocardium is more sensitive to ischemia than the subepicardium. The metabolic transmural gradients observed during in vivo ischemia were attributed to both variations in wall tension and collateral flow. Lowe et al. recently presented evidence that in addition to these variations the higher vulnerability of the subendocardium to ischemia could be secondary to an increased metabolic rate.

Topics: Adenosine Triphosphate; Animals; Collateral Circulation; Coronary Circulation; Coronary Disease; Creatine; Energy Metabolism; Lactates; Lactic Acid; Male; Myocardial Contraction; Myocardium; Oxygen Consumption; Perfusion; Phosphocreatine; Rats; Rats, Inbred Strains

When oxidative metabolism is inhibited in heart muscle, developed tension often increases slightly before decreasing below control. We have examined the possible mechanisms underlying these changes in developed tension in two series of experiments. In the first series of experiments, the photoprotein aequorin was used to monitor intracellular free [Ca2+] [( Ca2+]i) in papillary muscles during inhibition of oxidative phosphorylation, using either cyanide or hypoxia. The observed changes of developed tension were independent of changes in [Ca2+]i. It was therefore possible that these changes of tension were due to changes of intracellular pH (pHi). We tested this idea in a second series of experiments, using 31P nuclear magnetic resonance to monitor pHi, [ATP], and phosphocreatine concentration [( PCr]) in Langendorff-perfused ferret hearts. During the application of cyanide, pHi increased transiently before decreasing to below control. [PCr] decreased throughout this period, but [ATP] did not change. It is concluded that the observed changes of pHi could account for most of the observed changes of developed tension. It is suggested that the initial increase of pHi is due to PCr breakdown and the subsequent decrease of pHi to accelerated anaerobic glycolysis.

Topics: Acid-Base Equilibrium; Adenosine Triphosphate; Animals; Body Fluids; Calcium; Coronary Disease; Ferrets; Heart Ventricles; Hydrogen-Ion Concentration; Intracellular Fluid; Magnetic Resonance Spectroscopy; Myocardial Contraction; Papillary Muscles; Phosphates; Phosphocreatine; Sodium Cyanide

We applied 31P nuclear magnetic resonance to the study of acute ischemia in vivo. In open-chest rabbits, the left anterior descending coronary artery was occluded after control spectra were obtained. Phosphocreatine concentration decreased in the first minute and ATP concentration declined subsequently, and pH decreased to 5.8 within 20 min. Intracellular acidosis was greater than that previously reported for the isolated perfused rabbit heart.

Topics: Acid-Base Equilibrium; Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Energy Metabolism; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Phosphates; Phosphocreatine; Phosphorus Isotopes; Rabbits

Experiments were conducted on 18 dogs using an in situ blood-perfused canine heart model. Intracoronary infusion of AMP resulted in increased ATP and total adenine nucleotide levels. On reperfusion following a 15-min period of ischemia, ATP and total adenine nucleotide levels were significantly higher than control. Most important, contractile function recovered more rapidly in the AMP-treated dogs. It is therefore concluded that the delayed functional recovery noted after periods of ischemia is likely to be a direct result of delayed ATP resynthesis.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Coronary Disease; Creatine; Dogs; Energy Metabolism; Female; Male; Myocardial Contraction; Nitroprusside; Phosphocreatine

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Coronary Disease; Humans; Myocardium; Phosphocreatine

Hearts of chicks fed the creatine analog, 1-carboxymethyl-2-iminoimidazolidine (cyclocreatine), accumulated 15 mumol/g wet wt of the synthetic phosphagen, cyclocreatine-3-P; had total creatine levels reduced from the normal 6 mumol/g to only 1.8 mumol/g; and had their glycogen levels tripled. During total ischemia in vitro these hearts utilized the cyclocreatine-P for synthesis of ATP, had greatly prolonged glycolysis, and exhibited a two- to fivefold delay in depletion of both ATP and the total adenylate pool, relative to controls. Accumulation from the diet of comparable levels of the closely related 1-carboxyethyl-2-imino-3-phosphonoimidazolidine (homocyclocreatine-P) by heart was accompanied by only slight lowering of total creatine to 4.2 mumol/g, and a tripling of glycogen levels. During ischemia these hearts exhibited prolonged glycolysis, but they did not utilize the very stable homocyclocreatine-P (200,000-fold less reactive than creatine-P) and thus formed less Pi; most significantly, there was no delay in depletion of ATP levels relative to controls. Feeding of creatine doubled total creatine levels in heart, but had no marked effect on ATP depletion during ischemia; in all dietary groups creatine-P pools had fallen to less than or equal to 1.2 mumol/g by first tissue sampling. Although adaptive responses were also involved, maximal conservation of ATP and total adenylate pools in heart during ischemia apparently required, in addition to adequate glycogen reserves, substantial levels of a kinetically competent phosphagen that is thermodynamically poised to continue to assist glycolysis in buffering decreases and oscillations in the [ATP]/[free ADP] ratio at the lower phosphorylation potentials and more acid pH characteristic of later stages of ischemia. Decreases and oscillations in the [ATP]/[free ADP] ratio cannot be buffered effectively late in ischemia by the creatine-P system for thermodynamic reasons, or by the homocyclocreatine-P system because of kinetic limitations.

Topics: Adenine Nucleotides; Adenosine Triphosphate; Animals; Chickens; Coronary Disease; Creatinine; Glycogen; Imidazolidines; In Vitro Techniques; Kinetics; Male; Myocardium; Phosphocreatine; Thermodynamics

The effects of coronary arterial perfusion with a perfluorochemical substance (perfluorotributylamine) on the segmental myocardium of the beating heart were studied in 12 open chest anesthetized dogs. Following 10 min of left anterior descending coronary artery occlusion, perfusion of the coronary artery with the perfluorochemical returned myocardial function and metabolism toward control states, although myocardial diastolic properties as well as coronary venous PCO2 and lactate were not restored completely within 7 min after reperfusion. Perfluorochemicals may be of clinical importance in protecting the ischemic myocardium because of their oxygen carrying capacity together with favorable physiochemical properties for protection of the microcirculation.

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Blood Substitutes; Cardiac Output; Coronary Circulation; Coronary Disease; Dogs; Electrocardiography; Fluorocarbons; Heart; Heart Arrest, Induced; Heart Rate; Myocardial Contraction; Myocardium; Oxygen Consumption; Perfusion; Phosphocreatine

The association between phosphocreatine's antifibrillatory action and its effect on the excitement propagation processes in the ischemic area was investigated under acute coronary arterial occlusion in dogs. Ischemia considerably reduced the amplitude, and increased the duration and time of onset, in local electrograms, and provoked cardiac fibrillation at the time of occlusion or during the recovery of coronary flow. A single intravenous injection of 300 mg/kg phosphocreatine eliminated cardiac fibrillation and largely prevented electrographic changes in the ischemized area. Phosphocreatinine, phosphocreatine's structural analogue, produced a similar effect. It is suggested that antiarrhythmic action of phosphocreatine and phosphocreatinine is mediated by their membrane effects.

Topics: Acute Disease; Animals; Anti-Arrhythmia Agents; Coronary Disease; Dogs; Drug Evaluation, Preclinical; Heart Conduction System; Kinetics; Phosphocreatine; Ventricular Fibrillation

The effect of thiopental (100 mg X 1(-1] during total ischemia, low-flow ischemia, and severe hypoxia with maintained flow was investigated in the isolated perfused rat heart. During total ischemia the rate of decline of tissue creatine phosphate and adenosine triphosphate was no different in thiopental-treated and untreated hearts. The development of ultrastructural damage during total ischemia, the release of creatine kinase on reperfusion, and the exacerbation of ultrastructural damage after reperfusion were unaffected by thiopental. When thiopental was added to the perfusate during hypoxia and during low-flow ischemia at a normal pH(7.4), creatine kinase release during reoxygenation and during reperfusion was significantly less (P less than 0.005 and P less than 0.05, respectively) than in the untreated groups. After low-flow ischemia at a low pH (6.5), creatine kinase release was no different in thiopental-treated and untreated hearts. Thus, thiopental afforded protection of the myocardium in hypoxia and low-flow ischemia at pH 7.4 but not in total ischemia and low-flow ischemia at pH 6.5. The data are consistent with the hypothesis that during total ischemia and low-flow ischemia at pH 6.5, acidosis favors the entry of thiopental into the cell, causing inhibition of mitochondrial function and reduction of ATP production. During hypoxic perfusion and low-flow ischemia at pH 7.4, when the decrease in pH is less, the cardiodepressant effect of thiopental may offset any deleterious effect of the drug on intracellular organelles such as mitochondria.

Topics: Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Creatine Kinase; Hydrogen-Ion Concentration; Hypoxia; In Vitro Techniques; Mitochondria, Heart; Myocardium; Perfusion; Phosphocreatine; Rats; Rats, Inbred Strains; Thiopental

An important question in energy metabolism of the reperfused, previously ischemic myocardium is whether the return of a normal tissue adenosine triphosphate (ATP) content is a prerequisite for normal rates of oxygen consumption (that is, ATP turnover) and cardiac function. To study this problem, isolated working rat hearts were perfused with bicarbonate saline solution containing glucose (10 mM) at near physiologic work load. After 20 minutes, hearts were made totally ischemic by clamping the aortic and atrial lines for 5, 10 or 20 minutes and then were reperfused for another 10 minutes. Heart rate, aortic pressure, cardiac output and myocardial oxygen consumption were measured continuously. Adenine nucleotides, phosphocreatine, glycogen and the products of glycolysis were determined in freeze-clamped tissue extracts. Functional recovery was assessed by return of aortic pressure and oxygen consumption to preischemic values. Time required for return of function after reperfusion was 90 seconds after 5 minutes and 124 seconds after 10 minutes of ischemia. No recovery was observed after 20 minutes of ischemia. Tissue ATP content decreased significantly at the end of 5 (-38%) and 10 (-56%) minutes of ischemia and did not increase significantly at return of aortic pressure and oxygen consumption to preischemic values. Glycogen stores decreased by more than 50% at the end of 10 minutes of ischemia and did not normalize on recovery. In contrast to ATP or glycogen, the phosphocreatine content decreased to even lower levels at the end of ischemia, but returned to levels higher than the control level after recovery from 5 to 10 minutes of ischemia in association with return of function.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Energy Metabolism; Glycogen; Lactates; Male; Myocardium; Phosphocreatine; Rats

High-energy phosphate metabolites of the canine heart were analyzed before coronary artery occlusion and after 15 minutes of ischemia, and the results were then correlated with the occurrence of ventricular fibrillation upon reperfusion (RVF). Animals which developed VF upon reperfusion after 15 minutes of ischemia had lower levels of creatine phosphate and endocardial adenosine triphosphate (ATP), and increased accumulation of the catabolites of ATP metabolism, inosine and hypoxanthine. Animals which developed RVF also had lower levels of regional myocardial blood flow in the center of the ischemic zone during the period of coronary occlusion. Occluded bed size was the same in dogs which did and did not develop RVF. These data suggest that VF upon reflow is associated with more severe ischemia and an increase in high-energy phosphate catabolism during the period of ischemia.

Topics: Adenine Nucleotides; Animals; Blood Pressure; Coronary Circulation; Coronary Disease; Coronary Vessels; Dogs; Energy Metabolism; Heart Rate; Hypoxanthine; Hypoxanthines; Inosine; Ligation; Phosphates; Phosphocreatine; Ventricular Fibrillation

The mechanism of antiarrhythmic action of phosphocreatine on ischemic myocardium was studied by analyses of electrograms from normal and ischemic tissues. Ischemia induced significant changes in amplitude, duration, and conduction time of the electrograms, thereby showing depolarization of membranes and retarded conduction of excitation. Phosphocreatine administered in a single dose, 300 mg/kg iv, completely eliminated ventricular fibrillations in the ischemic hearts and significantly diminished the electrical instability occurring during reperfusion. The effects of phosphocreatine were completely reproduced by its structural analog phosphocreatine which is inactive in the creatine kinase reaction. It is concluded that the antiarrhythmic effect of both compounds is related to their specific chemical structure and that their specific effect is likely to be mediated via interaction with a sarcolemma site.

Topics: Animals; Anti-Arrhythmia Agents; Coronary Disease; Dogs; Electrocardiography; Phosphocreatine; Ventricular Fibrillation

Myocardial ischemia due to increased oxygen demand (pacing tachycardia plus critical coronary stenoses) alters diastolic distensibility and relaxation more than ischemia of comparable duration due to coronary occlusion. To investigate the relationship between myocardial diastolic function and metabolism, we compared myocardial high energy phosphate content, tissue pH, and regional blood flow for these two types of ischemia in anesthetized open-chest dogs. Myocardial biopsies were done with a high-speed air-turbine biopsy drill, permitting rapid (less than 1-second) freezing of tissue samples from both nonischemic and ischemic areas, while myocardial pH was measured with a hydrogen ion-selective polymer membrane implanted in the subendocardium. After 3 minutes of pacing tachycardia in dogs with critical coronary stenoses (demand-type ischemia, n = 14), regional systolic function (% segment shortening by ultrasonic crystals) was mildly depressed (from 19 +/- 2% control to 13 +/- 2% post-pacing, P less than 0.01), while left ventricular diastolic pressure-segment length relations shifted upward, indicating decreased distensibility of the ischemic myocardial segment. Associated with these changes in function, subendocardial adenosine triphosphate decreased (from 31.3 +/- 1.5 to 27.9 +/- 1.0 nmol/mg protein, P less than 0.01), as did creatine phosphate (53.8 +/- 2.1 to 39.6 +/- 2.5 nmol/mg protein, P less than 0.01), while myocardial pH declined slightly (delta pH = -0.14 +/- 0.02, P less than 0.01). In contrast, at 3 minutes of coronary artery occlusion (primary ischemia, n = 14), regional segment shortening was replaced by systolic bulging (% shortening decreased from 17 +/- 2% to -2 +/- 1% during occlusion, P less than 0.01), while left ventricular pressure-segment length relations were not shifted upward, and there was no decrease in diastolic distensibility of the ischemic segment. With coronary artery occlusion, subendocardial adenosine triphosphate declined slightly (33.2 +/- 0.5 to 29.2 +/- 2.0 nmol/mg, P less than 0.05), while creatine phosphate decreased substantially (51.1 +/- 2.3 to 7.8 +/- 1.4 nmol/mg protein, P less than 0.01). Myocardial pH fell strikingly (delta pH = -0.33 +/- 0.03, P less than 0.01), and the decline was 236% of that seen with demand-type ischemia. Regional myocardial blood flow (microsphere technique) showed a decreased endocardial:epicardial (endo:epi) ratio (1.04 +/- 0.04 control vs. 0.40 +/- 0.05 during pacing, P less than

Topics: Animals; Coronary Circulation; Coronary Disease; Dogs; Hemodynamics; Hydrogen-Ion Concentration; Myocardial Contraction; Myocardium; Nucleosides; Nucleotides; Oxygen Consumption; Phosphocreatine; Regional Blood Flow; Tachycardia

The possibility that myocardial ischaemia alters the defence mechanisms against oxygen toxicity has been investigated. Ischaemia was induced in isolated, perfused rabbit hearts by reducing coronary flow from 25 ml/min to 1 ml/min for 90 min. Two different degrees of ischaemic damage have been achieved using either spontaneously beating or electrically stimulated hearts. The effects of post-ischaemic reperfusion were also followed for 30 min. Tissue activity of superoxide dismutase (SOD), glutathione peroxidase and reductase (GPD and GRD) have been determined together with tissue content of reduced and oxidized glutathione (GSH and GSSG) and of protein SH groups. The changes in myocardial ATP and CP content and release of CPK and of GSH and GSSG were also determined. Systolic and diastolic pressures were continuously monitored. In the spontaneously beating hearts ischaemia induced a reduction of tissue GSH and protein SH groups. On reperfusion there was a recovery of mechanical function, a transient release of GSH into the coronary effluent and an increase of tissue GSH. In the paced hearts, ischaemia resulted in 50% reduction of mitochondrial SOD activity together with a reduction of tissue GSH and protein SH groups. Reperfusion induced a massive release of CPK and of GSH and GSSG, a further reduction of tissue GSH concomitant with an increase of GSSG and no recovery of mechanical function. GPD and GRD activity were not affected by ischaemia and reperfusion. These data indicate that severe ischaemia induces a reduction of the protective mechanisms against oxygen toxicity.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Glutathione; Glutathione Disulfide; Glutathione Peroxidase; Glutathione Reductase; Heart; In Vitro Techniques; Kinetics; Myocardium; Oxygen; Perfusion; Phosphocreatine; Rabbits; Superoxide Dismutase

Using the isolated perfused heart preparations of the rat, effects of diltiazem, a calcium antagonist, on the ischemic derangements of the mechanical function and the energy metabolism of the ventricular myocardium were studied. The myocardial tissue levels of creatine phosphate (CP), ATP, inorganic phosphate (Pi) and pH were determined with 31P-NMR. Global ischemia was induced by cross-clamping of the aortic inflow line for 15 min, which resulted in a fall of CP, ATP and pH and a rise of Pi. The test hearts were perfused with diltiazem-containing solution (10(-7), 10(-6) and 10(-5) M) for 12 min prior to the induction of the global ischemia. A significant dose-related decline of the myocardial mechanical function expressed as (left ventricular pressure) X (heart rate) was observed in diltiazem-treated hearts. In doses above 10(-6) M, diltiazem delayed the onset of the fall of the myocardial CP and pH levels and the rise of Pi induced by ischemia, and there was an excellent correlation between the suppression of the myocardial mechanical function observed before induction of ischemia and the level of the myocardial CP and pH at the initial phase of ischemia, indicating that the improvement of the myocardial energy metabolism was due to the cardiodepressant effects of the compound.

Topics: Animals; Benzazepines; Coronary Circulation; Coronary Disease; Diltiazem; Energy Metabolism; Heart; Heart Rate; Hydrogen-Ion Concentration; In Vitro Techniques; Magnetic Resonance Spectroscopy; Male; Myocardium; Perfusion; Phosphocreatine; Rats; Rats, Inbred Strains; Time Factors

The effect of phosphocreatine and phosphocreatinine on changes in crude lysophosphoglycerides (LPG) in the plasmatic membranes of canine heart, induced by short-term ischemia (an 8-minute-long occlusion of the left descending coronary artery), was examined. Ischemia caused a considerable rise in LPG level, with a mean 83% rise in lysophosphatidyl choline and a 168% rise in lysophosphatidyl ethanolamine. Intravenous administration of 300 mg/kg phosphocreatine or phosphocreatinine completely prevented the accumulation of LPG in the ischemic area. Since LPG have pronounced arrhythmogenic properties, the data obtained suggest that anti-arrhythmic activity of phosphocreatine and phosphocreatinine in acute myocardial ischemia results from the effect these substances have on membrane phospholipid metabolism in the ischemized area.

Topics: Animals; Coronary Disease; Dogs; Female; Glycerophosphates; Male; Membrane Lipids; Phosphocreatine

Topics: Adenosine Triphosphate; Coronary Disease; Humans; Myocardium; Phosphocreatine

The metabolic alterations induced, in the isolated rat heart, by graded ischaemia and reperfusion, were evaluated both by 31P-NMR spectroscopy and by biochemical analysis. The relative changes in phosphorylated compound contents measured by both methods were well correlated for ATP (r = 0.94) and Pi (r = 0.88), but less for PC (r = 0.72). These results demonstrate that the data drawn from the 2 methods compare well, for the assessment of the effects of ischaemia on the isolated heart. In order to characterize the extent or energetic alterations caused by ischaemia and reperfusion from the data drawn from a single NMR spectrum various indices have been calculated. A simple index (Formula: see text) seems to this regard, as discriminative as the adenylate charge or the phosphorylation potential.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Coronary Disease; Magnetic Resonance Spectroscopy; Myocardium; Perfusion; Phosphocreatine; Phosphorus; Rats; Rats, Inbred Strains

Administration of greater than or equal to 10 mg/kg isoproterenol in rats absolutely diminished local myocardial blood flow within 0.5 min continuing up to 45 min. The blood flow reduction was followed by an increased lactate content and a decrease of both the intracellular redox potential and the content of high energy phosphates in the myocardium. The graduation of the initial lactate accumulation in different myocardial regions corresponds to the myocardial distribution of the infarct-like necroses occurring 24 h later. The very early alterations are comparable with an absolute (blood flow reduction), irreversible, and acute ischemia. In the dose range from 0.05 to 1 mg/kg of isoproterenol, an acceleration of the local myocardial blood flow was caused which, however, was accompanied by ischemia-like disturbances, too. Therefore, this condition is considered as a relative ischemia, an increased but insufficient blood supply.

Topics: Animals; Blood Pressure; Coronary Circulation; Coronary Disease; Heart Rate; Heart Ventricles; Isoproterenol; Kinetics; Lactates; Male; Myocardium; Oxidation-Reduction; Phosphates; Phosphocreatine; Pyruvates; Rats; Rats, Inbred Strains

Hyperthyroid rat heart was studied with the purpose of identifying the mechanism for the significant decrease in total creatine (free creatine plus phosphocreatine) observed in this pathology and its consequences on heart function. Administration of L-thyroxine in doses of 50-100 micrograms/100 g of body weight during a week resulted in a reversible decrease of the total creatine by 40-50%. Simultaneously, remarkable changes in the creatine transport system across the cardiac cell membranes were observed: both the maximal rate of its active uptake and its passive movement along its concentration gradient were enhanced. In euthyroid hearts, the parameters of creatine uptake (Km approximately or equal to 0.05 mM, Vmax = 20 nmole/min/g dry weight) were similar to those for skeletal muscle and the passive movement of creatine was negligible. In hyperthyroid hearts the latter rate was enhanced to 0.4 mumole min/g dry weight, this showing reversible damages in the cell membrane structure induced by L-thyroxine. This conclusion is consistent with observed penetration of colloidal lanthanum into the cells of hyperthyroid hearts. Perfusion of hyperthyroid rat hearts with 50 mM creatine significantly restored creatine content in the cells, Hyperthyroid hearts with decreased creatine content were found to develop ischemic contracture more rapidly and in higher extent than the euthyroid hearts. Increased sensitivity to ischemic damage may be related to decreased efficiency of energy channeling via phosphocreatine pathway.

Topics: Animals; Cell Membrane; Coronary Disease; Creatine; Energy Metabolism; Hyperthyroidism; Kinetics; Myocardial Contraction; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains; Thyroid Hormones; Thyroxine; Time Factors

Topics: Adult; Aged; Coronary Disease; Female; Hemodynamics; Humans; Infusions, Parenteral; Male; Middle Aged; Myocardial Contraction; Phosphocreatine; Time Factors

The most important biochemical derangements in ischemic myocardium are the decrease of energy rich phosphates (ATP and phosphocreatine) and intracellular acidosis, both of which contribute to a rapid loss of the contractile function. How and to which extent the alterations of carbohydrate and lipid metabolism are involved in these derangements is briefly discussed. In conditions of oxygen restriction the synchronism between the cytosolic and mitochondrial phase of carbohydrate metabolism is disrupted and beta-oxidation of long chain fatty acids is prevented. Consequently less ATP and more lactate is produced and fatty acids accumulate together with their activation products, acyl CoA in particular. In ischemia free carnitine is also decreased and the carnitine dependent functions (acyl transfer across mitochondrial membrane and pyruvate and alpha ketoglutarate dehydrogenase stimulation) impaired. The meaning of the altered carnitine dependent functions is considered together with the possible (demonstrated and supposed) metabolic effects of carnitine administration in cardiac ischemia.

Topics: Acyl Coenzyme A; Acyltransferases; Adenosine Triphosphatases; Adenosine Triphosphate; Animals; Carnitine; Carnitine Acyltransferases; Coronary Disease; Fatty Acids; Fatty Acids, Nonesterified; Glucose; Humans; Mitochondria, Heart; Models, Biological; Myocardium; Oxygen Consumption; Phosphocreatine; Transferases

Tissue contents of intermediates of fatty acid metabolism were determined in isolated volume-overloaded rat hearts, 3 months after creation of an aorto-caval fistula. In the absence of any modification of blood carnitine, tissue levels of total carnitine were reduced by 33% in overloaded hearts compared to normal hearts. Total tissue CoA was unchanged. Fifteen minutes of whole-heart ischemia (i.e. a 50% reduction in coronary flow) did not increase levels of long-chain acyl esters of CoA and carnitine of the overloaded myocardium, in the presence of glucose as the only exogenous substrate. This was associated with lower than normal levels of long-chain acyl carnitine under normoxic conditions. The addition of exogenous palmitate (1.5 mM) resulted in an ischemia-induced accumulation of long-chain acyl-CoA and acyl carnitine in the overloaded heart although to a smaller extent than in the normal heart under similar perfusion conditions.

Topics: Acyl Coenzyme A; Adenosine Triphosphate; Animals; Cardiomegaly; Carnitine; Coenzyme A; Coronary Disease; Energy Metabolism; Fatty Acids; Female; Heart Failure; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains

The influence of prostacyclin (PGI2) alone or in combination with intraaortic balloon pumping (IABP) on the levels of energy-rich phosphate compounds was investigated before and after coronary artery ligation in canine myocardium. There was a higher level in creatine phosphate in the ischemic as well as non-ischemic areas of the myocardium after treatment with PGI2, however the most protective effect was registered after a combination of PGI2 and IABP. PGI2 also reduces the release of cathepsin D activity into the blood independently whether or not a mechanical support of the heart after coronary artery ligation was performed.

Topics: Animals; Assisted Circulation; Cathepsin D; Coronary Disease; Dogs; Epoprostenol; Female; Intra-Aortic Balloon Pumping; Male; Phosphocreatine

In ischemic myocardium the time course of nonesterified fatty acid (NEFA) accumulation was studied in relation to changes in regional metabolism and mechanics. In open-chest dogs a coronary artery was partially occluded for 120 min. In the ischemic myocardium no increase was observed in NEFA content within 10 min, whereas changes were found in regional shortening, high-energy phosphate content, and glucose arteriologcal venous difference. During prolonged ischemia NEFA content increased, the highest values being found in the inner and middle layers after 120 min (112 and 85 nmol X g-1, respectively; control values 30); the value in the outer layers after 60 min was 93 nmol X g-1. After 120 min of ischemia, accumulation of NEFA generally occurred when myocardial blood flow was below 0.3 ml X min-1 X g-1 and ATP content was below 10 mumol X g dry wt-1. Under these circumstances the individual NEFA with the highest relative increase was arachidonic acid. The present findings indicate that the changes in mechanical function and metabolism, as observed in myocardium rendered ischemic for 10 min, are not caused by increased NEFA content and that NEFA accumulation may partly result from hydrolysis of glycerophospholipids.

Topics: Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Dogs; Fatty Acids, Nonesterified; Female; Glycogen; Male; Models, Cardiovascular; Myocardium; Phosphocreatine; Regional Blood Flow; Time Factors

31P Nuclear Magnetic Resonance (NMR) spectroscopy was used, in combination with biochemical methods, to describe the persisting alterations in energy metabolism provoked by graded normothermic (37 degrees C) global ischaemia, and reperfusion in the isolated perfused rat heart. Graded global ischaemia was induced by adjusting the coronary flow to 0, 1.2, 2.8, or 6.5% of the spontaneous coronary flow in hearts perfused retrogradely under 100 cmH2O (9.807 kPa) perfusion pressure. The 24 min ischaemia was followed by 30 min reperfusion with spontaneous coronary flow. Other series of hearts were perfused with a glucose-free buffer, they were submitted to identical restrictions of coronary flow but for 9 min only with a reperfusion of 20 min. NMR spectra (3 min) were taken throughout the perfusion-ischaemia-reperfusion sequence and used to follow the time-changes in intracellular pH and in the intramyocardial levels of phosphate compounds. Hearts were freeze-clamped at the end of reperfusion to allow for biochemical measurements to be made. Analysis of the results was mainly focused on the energy state at the end of reperfusion. At the end of ischaemia, the extent of the decrease in intracellular pH and the changes in phosphate compound levels were sharply dependent on the degree of coronary flow restriction. In glucose-free perfused hearts, the intracellular acidosis was less than in the presence of glucose. At the end of reperfusion, three kinds of metabolic alterations could be distinguished: 1) those, such as the extent of rephosphorylation of creatine, which were undiscriminative of the acuteness of the previous ischaemia; 2) those, such as the degree of the persisting depletion in ATP (and in the sum of adenine nucleotides), which were directly correlated to the degree of restriction of ischaemic coronary flow; 3) and those which characterised only the most severe conditions of ischaemia, namely a persisting increase in myocardial inorganic phosphate content, a residual shift, albeit slight, of intracellular pH toward acidic values and a displacement of the adenylate charge below control value. The assumption is made that these latter indices can be used to differenciate between reversible and irreversible metabolic damage. An index, calculated from NMR data and correlating well with the adenylate charge, is proposed.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Energy Metabolism; Female; Hydrogen-Ion Concentration; In Vitro Techniques; Magnetic Resonance Spectroscopy; Male; Myocardium; Perfusion; Phosphates; Phosphocreatine; Rats; Rats, Inbred Strains

The effect of ischaemia on the concentration of active pyruvate dehydrogenase complex has been investigated in glucose perfused hearts of normal rats fed a normal diet or a high fat diet or starved for 48 h; and in hearts from alloxan-diabetic rats. Global ischaemia induced by low flow (approx. 1 ml/min) lowered the concentration of active complex under most of the experimental conditions employed. Parallel studies showed that anoxia and K+ arrest of the heart had effects similar to that of ischaemia and suggested that hypoxia and decreased mechanical activity of the heart may be responsible for effects of low flow ischaemia. Evidence is reviewed that the effects of low flow ischaemia, K+ arrest and anoxia may be mediated through activation of pyruvate dehydrogenase kinase by increased reduction of mitochondrial NAD+. In hearts of normal rats on a normal diet, global ischaemia induced by zero flow and regional ischaemia induced by coronary artery ligation increased the concentration of active complex. Evidence is given that this may result from a combination of anoxia and acidosis. In aerobic perfusions at 60 mmHg, concentrations of active complex were ranked in the order: normal diet greater than high fat diet greater than 48 h starved greater than alloxan diabetic. This order was maintained when the concentration of active complex was increased by perfusion at 120 mmHg or lowered by global ischaemia induced by zero flow.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Diabetes Mellitus, Experimental; Dietary Fats; Heart Arrest; Lactates; Lactic Acid; Male; Myocardium; Oxygen Consumption; Perfusion; Phosphocreatine; Pyruvate Dehydrogenase Complex; Rats; Rats, Inbred Strains; Starvation

Metabolic and functional recovery following 60 minutes of low flow (0.1 ml/min) ischemia were compared in rabbit hearts perfused with normal sodium and potassium, low sodium (120 mM NaCl replaced by 120 mM LiCl), or zero potassium perfusate during ischemia. During the control, pre-ischemic, and reperfusion periods, all hearts were perfused identically with normal sodium and potassium. 31P NMR was used to monitor intracellular pH (pHi), ATP, and phosphocreatine (PGr). Developed pressure, end diastolic pressure, pHi, and the integrated areas of ATP and PCr were equivalent in the three groups in the pre-ischemic period. The fall in pHi, PCr, ATP, and developed pressure and the rise in end diastolic pressure during 60 min ischemia also did not differ among the three groups. In contrast to the lack of an effect of perfusate sodium and potassium on the decline in parameters of metabolism and function during ischemia, there was a marked difference in the recovery of these indices during reperfusion. Hearts perfused with low sodium during ischemia exhibited the best recovery (expressed as percent of control) of developed pressure (95 +/- 4%), PCr (106 +/- 6%), and ATP (51 +/- 2%) and the smallest rise in end diastolic pressure (229 +/- 50%); hearts perfused with normal sodium and potassium during ischemia had intermediate recovery values for developed pressure (53 +/- 10%), PCr (78 +/- 9%), ATP (45 +/- 4%) and end diastolic pressure (487 +/- 73%) and the hearts perfused with zero potassium solution during ischemia exhibited the poorest recovery of developed pressure (23 +/- 6%), PCr (49 +/- 6%), ATP (39 +/- 5%) and end diastolic pressure (968 +/- 185%).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Heart; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Myocardium; Perfusion; Phosphocreatine; Potassium; Rats; Sodium

The mechanism of irreversible damage to ischemic myocardium was investigated in the perfused rat heart. The time of transition from reversible to irreversible damage to contractile function was accelerated by accumulation of glycolytic products and increases in extracellular calcium. Both of these effects were largely independent of adenine nucleotide levels in the tissue. With zero coronary flow and 1.25 mM calcium the decrease in ability of the heart to recover ventricular function with reperfusion after 30 minutes of ischemia was directly correlated with accumulation of glycolytic products (as estimated by tissue lactate) during ischemia. The extent of lactate accumulation during ischemia was varied by preperfusing the hearts for 0, 10, or 15 minutes under anoxic, high coronary flow conditions to deplete tissue glycogen prior to ischemia, and by adding lactate back to the perfusate of these hearts during the ischemic period. Recovery of ventricular function was inversely related to tissue lactate during ischemia and varied from 28 to 92%, even though there was little or no change in tissue levels of residual adenosine triphosphate. Increasing extracellular calcium accelerated the time of onset of irreversible damage with little or no change in residual adenosine triphosphate levels. At any given calcium concentration, the time-dependent declines in the ability of the heart to recover ventricular function was also largely independent of adenosine triphosphate levels. These studies suggest a major role of anaerobic glycolytic products (lactate, hydrogen ion, or NADH) in ischemic damage to the heart that is unrelated to loss of tissue adenine nucleotides. With zero or low flow ischemia, this effect may result in irreversible damage to the myocardium before adenine nucleotides are reduced to critically low levels.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Calcium; Coronary Circulation; Coronary Disease; Glycolysis; Hypoxia; In Vitro Techniques; Lactates; Lactic Acid; Male; Myocardium; Perfusion; Phosphocreatine; Rats; Rats, Inbred Strains

Topics: Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Male; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains

Knowledge of metabolic changes in ischaemic myocardium is vital to the understanding of pathophysiological relations. The altered metabolic conditions in the myocardium during ischaemia are helpful in the diagnosis of coronary heart disease, but quantitative statements are as yet only possible under certain conditions. Reestablishment of the myocardial oxygen supply is essential in immediately influencing myocardial metabolism. Thrombolysis is therefore a theoretically sound measure in myocardial infarction, but proof of clinical efficacy has yet to be provided, probably because of critical durations of ischaemia.

Topics: Adenosine Triphosphate; Animals; Calcium; Catecholamines; Combined Modality Therapy; Coronary Circulation; Coronary Disease; Energy Metabolism; Heart; Heart Conduction System; Humans; Myocardial Infarction; Myocardium; Oxygen Consumption; Phosphocreatine; Rats; Sympathetic Nervous System

We used phosphorus-31 nuclear magnetic resonance to test the ability of a perfluorocarbon blood substitute that has been shown in previous studies to improve oxygen delivery to hypothermic myocardium to maintain aerobic high-energy phosphate metabolism during total global ischemia. Twenty-three isolated perfused rabbit hearts were subjected to 180 min of hypothermic (23 degrees C) global ischemia followed by 45 min of normothermic reperfusion. Hearts received multiple doses of a cardioplegic solution that contained either oxygenated perfluorocarbon (Fluosol O2), nonoxygenated perfluorocarbon (Fluosol N2), or standard crystalloid hyperkalemic cardioplegic solution (STD-KCl) at 30 min intervals. Recovery of isovolumic left ventricular developed pressure (LVDP) was used to assess preservation of contractile function. Recovery of LVDP was 84 +/- 19% of preischemic control values with Fluosol O2, 68 +/- 16% with Fluosol N2, and 67 +/- 17% with STD-KCl (p = .058 vs Fluosol N2 and p = .056 vs STD-KCl). During 3 hr of ischemia intracellular pH (pHi) fell to 6.68 +/- 0.20 with STD-KCl and to 6.71 +/- 0.14 with Fluosol N2 but remained above 7.00 throughout the ischemic period with Fluosol O2 (p less than .0001 vs Fluosol N2 or STD-KCl). Myocardial ATP content was better preserved at 107 +/- 14% of control values with Fluosol O2 compared to 60 +/- 18% of control with Fluosol N2 and 75 +/- 21% of control with STD-KCl (p less than .001 vs Fluosol N2, p = .002 vs STD-KCl). Phosphocreatine (PCr) was also better preserved with Fluosol O2.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Animals; Blood Substitutes; Coronary Disease; Energy Metabolism; Female; Fluorocarbons; Heart Arrest, Induced; Hydrogen-Ion Concentration; Myocardial Contraction; Oxygen; Perfusion; Phosphocreatine; Rabbits; Time Factors

The effects of severe global ischemia on cardiac high energy phosphate (HEP) stores were investigated in an in vitro rat model. The heart was removed from the rat in this model, sealed in a plastic bag and incubated for varying times and temperatures (20-45 degrees C). The rat, in the in vivo anoxic model, was subjected to cervical dislocation which resulted in respiratory arrest. In both models the hearts were removed and analyzed for HEP at appropriate times following the onset of anoxia or ischemia. Verapamil and nifedipine, administered intravenously 10 minutes before the start of the experiments, preserved HEP stores in both models. The degree of protection provided by the Ca+2 blockers was related to both the dose of drug and the duration of the ischemia/anoxia. Verapamil was more active than nifedipine in both models.

Topics: Adenine Nucleotides; Animals; Calcium Channel Blockers; Chromatography, High Pressure Liquid; Coronary Disease; Disease Models, Animal; Hypoxia; In Vitro Techniques; Male; Nifedipine; Phosphocreatine; Rats; Rats, Inbred Strains; Temperature; Verapamil

To elucidate determinants of reperfusion ventricular fibrillation (VF), regional myocardial blood flow, ATP, creatine phosphate (CP), heart rate and blood pressure were compared in 2 groups of anesthetized dogs: those that fibrillated spontaneously upon release of a 15-minute coronary artery occlusion (VF group, n = 8) and those that did not fibrillate when reperfused (No VF group, n = 27). Arterial pressure and heart rate before and during coronary artery occlusion were similar in both groups. Ischemic endo- and epicardial ATP values, measured at the end of the occlusion period, were reduced approximately 20% of nonischemic values in both groups. In contrast, CP (nmol . mg protein-1) within the ischemic zone was significantly lower in the VF group in both the epicardium (14.3 +/- 1.6 in the VF group vs 22.8 +/- 2.5 in the No VF group, p less than 0.01) and the endocardium (9.0 +/- 2.0 in the VF group vs 18.7 +/- 1.8 in the No VF group, p less than 0.01). Furthermore, epi- and endocardial regional myocardial blood flow in the center of the ischemic zone during occlusion was significantly lower in VF dogs than in No VF dogs. Epicardial flow was 0.06 +/- 0.03 ml X min-1 X g-1 in VF dogs vs 0.44 +/- 0.06 in No VF dogs (p less than 0.001) and endocardial flow was 0.03 +/- 0.02 ml X min-1 X g-1 in VF dogs vs 0.23 +/- 0.04 ml X min-1 X g-1 in No VF dogs (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Coronary Circulation; Coronary Disease; Dogs; Female; Heart Rate; Humans; Male; Phosphocreatine; Retrospective Studies; Time Factors; Ventricular Fibrillation

Ischemic injury to the heart in the period between aortic cross-clamping and administration of cardioplegic solution was evaluated in the normothermic rat heart model. After isolation and control perfusion with oxygenated Krebs-Henseleit bicarbonate buffer, the hearts were given lactated Ringer's cardioplegic solution (30 mEq of K+ per liter) for 2 minutes at three different intervals following aortic clamping: no delay, 2-minute delay, and 5-minute delay. Thereafter, the hearts were left unperfused and the time to initiation of ischemic contracture was recorded. Adenosine triphosphate (ATP) and creatine phosphate levels were measured in all groups prior to and at the conclusion of cardioplegia administration. A 2-minute delay in the administration of cardioplegic solution resulted in significantly lower (p less than 0.001) ATP levels that were restored after 2 minutes of cardioplegia administration. Contracture times were not significantly altered. A 5-minute delay resulted in significantly shorter (p less than 0.001) contracture times and significantly lower (p less than 0.001) ATP levels that were not restored to preischemic levels by 2 minutes of cardioplegia administration. The fate of the myocardium may be insensitive to events that occur during the earliest moments of ischemia provided that rapid administration of oxygenated potassium cardioplegia follows the ischemic period and restores preischemic high-energy phosphate stores. However, there is a critical ischemic time during the initial interval before cardioplegia that is associated with an impaired ability of the myocardium to tolerate subsequent ischemia.

Topics: Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Heart; Heart Rate; In Vitro Techniques; Male; Myocardial Contraction; Myocardium; Perfusion; Phosphocreatine; Potassium; Potassium Compounds; Rats; Rats, Inbred Strains

We measured indices of energy metabolism in tissue samples taken from the interventricular septum and left ventricular free wall of open-chest dogs under control conditions and after a 20-second period of no coronary inflow. The heart was paced at 150 beats/min, and arterial pressure was controlled by aortic constriction. Each tissue sample was divided into three transmural regions and analyzed for creatine phosphate, adenosine triphosphate, and lactate. Data were also obtained in animals subjected to ventricular fibrillation, with ventricular pressures reduced to atmosphere and sampling delayed to 70 seconds, and with the pulmonary artery constricted prior to coronary artery occlusion. In control animals, there were no metabolite differences between the free wall and septum. Coronary occlusion produced a lactate gradient across both the free wall and septum, with the highest lactate concentrations occurring in the regions adjacent to the left ventricular cavity. The increase in tissue lactate above control was greater in the septum than in the free wall. Coronary occlusion decreased tissue creatine phosphate but not adenosine triphosphate. The decrease in creatine phosphate was greater in the septum than in the free wall. Coronary occlusion and ventricular fibrillation, or coronary occlusion and ventricular pressures reduced to atmosphere, produced neither transmural metabolite differences nor differences between the free wall and septum. Pulmonary artery constriction increased right and decreased left ventricular pressures.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Animals; Arterial Occlusive Diseases; Blood Pressure; Coronary Disease; Dogs; Energy Metabolism; Heart Septum; Heart Ventricles; Lactates; Male; Phosphates; Phosphocreatine; Pulmonary Artery

Calcium antagonists potentially prevent ATP breakdown, but literature data on this subject are conflicting. We studied the effect of diltiazem on ATP catabolism in rat heart, perfused according to Langendorff. Administration of the drug took place either before or during ischemia, induced by lowering the perfusion pressure. The reduction in flow without diltiazem was 85%. We observed a significantly (P less than 0.001) lower production of purine nucleosides and oxypurines by the ischemic heart, when we gave diltiazem in a dose range of 1 to 100 microM before ischemia. The highest drug concentration reduced purine release by 85%. Due to ischemia, myocardial adenine nucleotide content decreased by 40% (P less than 0.001); this was partially prevented by 5 microM diltiazem (P = 0.4 v. untreated hearts). The drug also effectively reduced purine release, when applied five minutes after the induction of ischemia, but higher concentrations were needed.

Topics: Adenine Nucleotides; Adenosine; Adenosine Triphosphate; Animals; Benzazepines; Coronary Circulation; Coronary Disease; Diltiazem; Heart; Hypoxanthine; Hypoxanthines; In Vitro Techniques; Inosine; Male; Myocardium; Perfusion; Phosphocreatine; Rats; Rats, Inbred Strains; Uric Acid; Xanthine; Xanthines

During myocardial ischaemia the purine (ATP, GTP) and pyrimidine (CTP, UTP) nucleotide content of the myocyte falls. When the ischaemic episode resolves, many hours or even days are required for restoration of nucleotide pools. These observations suggest that repetitive episodes of ischaemia might produce progressive depletion of nucleotide pools. In order to determine the effect of repetitive episodes of brief ischaemia on nucleotide pools, open-chest dogs underwent three 12 min periods of occlusion of the left anterior descending coronary artery, with each occlusion followed by 10 min of reperfusion. During the first occlusion nucleotide pools decreased by 30% (ATP); 36% (GTP), 52% (CTP), and 48% (UTP). The subsequent two occlusions produced no further decrease in nucleotide pools. The myocardial content of adenine nucleotide catabolites (adenosine + inosine + hypoxanthine) tended to be greater during the first occlusion than during the subsequent occlusions, and substrate delivery (ie regional myocardial blood flow) was similar during each of the periods of ischaemia. These results indicate that a decrease in the rate of nucleotide degradation, rather than an increase in nucleotide synthesis, accounts for the maintenance of nucleotide content during subsequent ischaemic episodes after the initial ischaemic period. Thus repetitive episodes of regional ischaemia do not produce a cumulative decrease in the high energy phosphate content of the myocardium.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Coronary Disease; Cytidine Triphosphate; Dogs; Guanosine Triphosphate; Ligation; Myocardium; Perfusion; Phosphocreatine; Purine Nucleotides; Pyrimidine Nucleotides; Recurrence; Uridine Triphosphate

The direct myocardial protection afforded by three structurally distinct calcium antagonists (0.1 micron nifedipine, 0.1 micron verapamil and 0.4 micron diltiazem), and a calmodulin antagonist (20 micron W-7) was assessed in isolated working rat hearts subjected to 30 min global ischaemia followed by 30 min reperfusion. At these concentrations, no drug-induced cardiac depression nor coronary vasodilatation was observed prior to ischaemia. All four agents improved recovery of cardiac function (assessed as total cardiac output) on reperfusion (by 49%, 29%, 64% and 72% respectively, compared to controls), attenuated the release of lactate dehydrogenase (by 52%, 55%, 65% and 66% respectively) and inhibited intracellular 45Ca accumulation (by 42%, 35%, 49% and 45% respectively). Despite the increased tissue calcium and enzyme leakage in reperfused hearts, the [3H]inulin-impermeable space was not decreased, suggesting specific changes in membrane permeability rather than partial sarcolemmal rupture. Drug treatment did not alter the rate nor extent of high-energy phosphate depletion during ischaemia, thus eliminating ATP preservation and negative inotropy as mechanisms for the protective effects observed in this system. Improved restoration of coronary flow was obtained in treated hearts but we believe this was more likely to be a consequence of myocardial protection rather than direct coronary vasodilatation. Thus, the beneficial effects observed probably resulted from direct preservation of cellular viability. When given only during the reperfusion phase, nifedipine and W-7 were almost as effective as when given before ischaemia, whereas verapamil and diltiazem were inactive. This highlights differences between the various structural subclasses of calcium antagonists. Furthermore, the efficacy of the calmodulin antagonist, W-7, in this system suggests a possible key role for calmodulin-activated enzymes in the progression of reperfusion damage.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Calcium; Calcium Channel Blockers; Calmodulin; Cardiac Output; Coronary Circulation; Coronary Disease; Diltiazem; L-Lactate Dehydrogenase; Male; Myocardium; Nifedipine; Perfusion; Phosphocreatine; Rats; Rats, Inbred Strains; Sulfonamides; Verapamil

The effect of flow-induced ischemia on the rate of pyruvate decarboxylation and the activation state of the pyruvate dehydrogenase multienzyme complex was investigated in the isolated, perfused rat heart. Pyruvate dehydrogenase activity in the heart decreased significantly during flow-induced ischemia and was a function of changes in the activation state (i.e., active/total activity) of the enzyme complex. In the absence of pyruvate, the activation state of pyruvate dehydrogenase decreased from nearly 100% active at the normal flow rate (10 ml/min) to 20% active as the flow was reduced to 0.5 ml/min. At high pyruvate levels (5 mM), the activation state increased from nearly 70% active at control flow rates to 100% active during ischemia. At an intermediate pyruvate concentration (0.5 mM), the enzyme complex was maintained at a relatively low activation state (30-35% active) throughout the range of flow rates tested. Ischemia caused elevated perfusate lactate concentrations only when the flow rates were less than 5.0 ml/min. The activation state of the pyruvate dehydrogenase complex in hearts perfused with glucose was also decreased during ischemia.

Topics: Adenine Nucleotides; Animals; Coronary Disease; Enzyme Activation; In Vitro Techniques; Kinetics; Male; Myocardium; Perfusion; Phosphocreatine; Pyruvate Dehydrogenase Complex; Rats; Rats, Inbred Strains

A new procedure is described which allows for the rapid homogenisation, extraction and analysis of the metabolite content of microbiopsy samples (milligram quantities) while completely overcoming the major errors arising as the consequence of the substantial and variable tissue loss associated with conventional procedures. In addition to allowing more accurate and faster analysis of much smaller quantities of tissue the procedure also allows for the coincident paired measurement of flow (radioactive microspheres) in each biopsy. An example of the application of the method to the measurement of flow and high energy phosphate content in multiple microbiopsy samples from normal and ischaemic canine myocardium is provided.

Topics: Adenosine Triphosphate; Animals; Biopsy; Coronary Disease; Dogs; Isotope Labeling; Microspheres; Myocardium; Phosphocreatine; Radioisotopes; Tissue Extracts

Samples of myocardium with varying degrees of ischemia were obtained from subendo- and subepicardium of nonischemic, ischemic border and center zones of canine left ventricles to assess the sequence of rapid alterations of several parameters of energy metabolism induced by myocardial ischemia. Ischemia was induced by occluding the left anterior descending coronary artery. The contents of creatine phosphate (CP) and ATP decreased significantly. There was a significant accumulation of lactate. The redox potential (Eh) and phosphorylation potential (l') also decreased sharply, but only a slight decrease in energy charge (E.C.) was noted. A close correlation was found between ATP and total adenine nucleotide (r = 0.99). There were various degrees of linear correlation between other parameters, except for ATP (and total adenine nucleotide) and Pi, and CP and l', which were uncorrelated. The sequence of rapid alterations in the parameters of energy metabolism induced by ischemia was: (1) l' and CP, (2) Pi, ATP and Eh, and finally (3) lactate and E.C. A significant increase of the heart rate and a decline of the mean blood pressure and left ventricular pressure (LVP) were also observed in association with a slight change in the maximum rate of rise of the left ventricular pressure (dP/dtmax).

Topics: Adenine Nucleotides; Adenosine Triphosphate; Animals; Blood Pressure; Coronary Disease; Dogs; Energy Metabolism; Heart Rate; Hemodynamics; Lactates; Myocardium; Oxidation-Reduction; Phosphocreatine; Phosphorylation

This study was aimed to evaluate the effect of catecholamine on the myocardium reperfused after hypothermic global ischemia, by changes of hemodynamics, biochemistry and ultrastructure. Under cardiopulmonary bypass (CPB) at flow rate 80 ml/kg/min., the aorta was clamped for 60 min. at 28 degrees C of myocardial temperature and reperfused for 60 min. in 26 mongrel dogs. They were divided into 4 groups by infusion of physical saline solution (control), epinephrine 1 microgram/kg/min. (group 1), epinephrine 0.1 microgram/kg/min. (group 2) and dobutamine 5 micrograms/kg/min. (group 3) during reperfusion. The hemodynamic parameters and myocardial isoenzyme (m-AST, MB-CPK) of coronary sinus venous blood were measured before CPB, 30 and 60 min. after declamp. The myocardial adenosine triphosphate (ATP), creatine phosphate (CP), water content, tissue Ca content and fine structure with score of mitochondrial membrane and cristae were examined in epicardium and endocardium at the end of experiment. Hemodynamic parameters after declamp were higher in group 1, 2 and 3 than control (p less than 0.05). The water content and tissue Ca content in group 1 were higher than control. The ATP of endocardium was lowest but CP was no significant difference among four groups. The mitochondrial score in group 1 was lower than control. These data suggest that epinephrine and dobutamine increase hemodynamics and tissue Ca content on the reperfused myocardium following 60 min. of hypothermic global ischemia, but they do not improve depletion of ATP and disruption of myocardial ultrastructure. High dose of epinephrine accentuates ischemic damage of reperfused myocardium after hypothermic global ischemia.

Topics: Adenosine Triphosphate; Animals; Body Water; Catecholamines; Coronary Disease; Creatine Kinase; Dobutamine; Dogs; Epinephrine; Hemodynamics; Hypothermia, Induced; Isoenzymes; Myocardium; Perfusion; Phosphocreatine

Verapamil may protect ischemic myocardium by several mechanisms: prevention of Ca overload as a direct effect of blocking Ca influx through slow channels, coronary vasodilatation, decreased contractility, or cardioplegia produced by high doses. We manipulated the experimental situation to ask whether the first mechanism alone could be protective. We studied isovolumically contracting rabbit hearts perfused at 37 degrees C, paced at 150/min, and maximally vasodilated by dipyridamole. Hearts were subjected to 60 min of low flow ischemia followed by 60 min reperfusion. Two groups were exposed to verapamil 0.5 microM beginning either 2 to 4 min before ischemia or 10 min after the onset of ischemia (when pressure development had ceased) and continuing until reperfusion. Developed pressure recovered during reperfusion to 70 +/- 4% of its initial value in hearts treated with verapamil before ischemia compared to 40 +/- 5% for control hearts and 35 +/- 11% for hearts treated with verapamil 10 min after the onset of ischemia. There was significant preservation of phosphocreatine at 10 min of ischemia and of ATP at 60 min in the early verapamil group compared to the other two. When verapamil was present before ischemia, pressure development during early ischemia was reduced to about 50% of control. Consequently there was substantial sparing of high energy phosphates and enhanced recovery of mechanical function. If verapamil was added 10 min after the onset of ischemia, when it no longer could affect cardiac work, there was no protection. Therefore, in the isolated rabbit heart, verapamil had an important protective effect only by reducing contractility of ischemic myocardium.

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Calcium; Coronary Disease; Creatine; In Vitro Techniques; Ion Channels; Male; Myocardial Contraction; Phosphocreatine; Rabbits; Strontium Radioisotopes; Vasodilation; Verapamil

The effect on the recovery of mechanical function, ATP, phosphocreatine, Pi and pH of various lengths of total global ischaemia in the insulin-treated, perfused rat heart has been studied using 31P-NMR. Insulin-treated hearts recovered stable mechanical function after 18 min ischaemia when their intracellular pH was 6.0 and 70% of the pre-ischaemic ATP remained. Hearts perfused without insulin fail to recover after 18 min ischaemia, having an intracellular pH of 6.3 and 40% of ATP remaining (Bailey, I.A., Seymour, A.-M.L. and Radda, G.K. (1981) Biochim, Biophys. Acta 637, 1-7). Thus, ATP maintenance in ischaemia is more important to recovery on reperfusion than is maintaining intracellular pH. The importance of this observation in devising biochemical strategies for the clinical protection of the myocardium is discussed.

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Coronary Disease; Heart; Hydrogen-Ion Concentration; Insulin; Kinetics; Magnetic Resonance Spectroscopy; Male; Myocardial Contraction; Phosphates; Phosphocreatine; Rats; Rats, Inbred Strains

Guinea pig hearts, perfused with (5-3H) glucose (8 mmol . litre-1) and subjected to 30 min of reduced (6%) coronary flow, exhibited two distinctly different metabolic and electrophysiological responses to ischaemia. In 22 of the 50 hearts studied (Group 1) glucose utilisation declined during ischaemia from 2.5 +/- 0.2 to 1.3 +/- 0.2 mumol . litre-1 . g-1 dry wt. In these hearts, endogenous substrates such as glucogen and triglyceride were mobilised and, although input into glycolysis may have been initially increased through accelerated glycogenolysis, estimated glycolytic flux (1.7 +/- 0.1 mumol hexose . min-1 . g-1 dry wt) remained limited. Instead, there was a large accumulation of the intermediates of glycolysis, an increase in the content of AMP and cAMP and a particularly marked decline in creatine phosphate levels. With subsequent reperfusion, these hearts all fibrillated. In contrast, in the other 28 hearts (Group 2) glucose utilisation (5.1 +/- 0.4 mumol . min-1 . g-1 dry wt) and estimated glycolytic flux (4.1 +/- 0.01 mumol hexose . min-1 . g-1 dry wt) were increased during ischaemia. In these preparations, relatively little glycogen and triglyceride were utilised, and there was less accumulation of glycolytic intermediates. Further, lower levels of AMP and cAMP were observed and creatine phosphate: creatine ratios were better maintained. These hearts did not fibrillate during reperfusion. Thus the variable susceptibility of the myocardium to ischaemic damage, as evidenced by the random incidence of ventricular fibrillation during reperfusion, may have been related to two distinctly different metabolic responses to restricted perfusion.

Topics: Adenine Nucleotides; Animals; Coronary Disease; Glucose; Glycogen; Guinea Pigs; Male; Myocardium; Oxygen Consumption; Perfusion; Phosphocreatine; Triglycerides; Ventricular Fibrillation

Calcium antagonists may protect the myocardium against the consequences of ischemia. Phosphorus-31 nuclear magnetic resonance (31P NMR) was used to study the effect of nifedipine on intracellular acidosis and high energy phosphate depletion during global ischemia. Isolated rat hearts were paced (300 beats/min), perfused with a modified Tyrode solution for 30 min, made totally ischemic for 30 min (37 degrees C) and then reperfused for 30 min. When required, nifedipine (1 mg/l) was added to the perfusion fluid 10 min before ischemia. During ischemia intracellular pH fell from 7.11 +/- 0.03 (mean +/- S.E.M.) to 5.88 +/- 0.04 in the untreated hearts (n = 6), and from 7.11 +/- 0.03 to 5.95 +/- 0.02 in the treated hearts (n = 6). During the first 20 min of ischemia, intracellular pH was significantly higher in the treated than in the untreated hearts (P less than 0.001). Myocardial creatine phosphate (CP) content was depleted after 15 min of ischemia in the untreated hearts, and after 20 min of ischemia in the hearts treated with nifedipine. Myocardial adenosine triphosphate (ATP) content was depleted after 20 min of ischemia in the untreated hearts; ATP content in hearts that received nifedipine amounted to 23.5 +/- 6.2% of control after 30 min of ischemia. In contrast with the untreated hearts, the nifedipine-treated hearts showed a rapid recovery of CP content during reperfusion. The results indicate that nifedipine protects the myocardium against the metabolic consequences of ischemia and reperfusion.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Magnetic Resonance Spectroscopy; Male; Myocardium; Nifedipine; Phosphocreatine; Phosphorus Isotopes; Rats; Rats, Inbred Strains

The onset of global myocardial ischemia was related to mechanical function (intraventricular pressure), cellular redox state (NADH fluorophotography), and high energy profile (phosphorous-31 nuclear magnetic resonance). Ten rabbit hearts were excised and perfused on a modified Langendorff apparatus (37 degrees C; pO2 480 Torr). Developed pressure and positive and negative dp/dt were determined at control, 1-10, 15, 30, 45, and 60 sec of acute global ischemia. NADH fluorophotographs were taken at control, 1-10, 15, 20, 30, 60 sec, and 5, 10, and 30 min. P-31 NMR spectra in 14 guinea pig hearts under identical conditions were obtained at control, 1, 5, 10, 20, 40, and 60 min of acute global ischemia. LV contractility diminished within 1 sec (P less than 0.01) of ischemia and dropped to less than 35% of control by 1 min. Reduction of mitochondria was detected by epicardial NADH fluorophotography at 2 sec of ischemia. Cellular pH diminished 0.3 pH units by 5 min. Adenosine triphosphate (ATP) concentration remained at control levels while phosphocreatine (PCr) dropped to 63 +/- 8.5% of control by 1 min of ischemia.. After the onset of global ischemia (1) mitochondrial electron transport ceases by 2 sec; (2) acidosis develops immediately; (3) LV contractility diminishes by 1 sec; (4) ATP concentration appears to be buffered by PCr, and is dissociated from myocardial function.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Heart Ventricles; Magnetic Resonance Spectroscopy; Myocardial Contraction; NAD; Oxidation-Reduction; Phosphates; Phosphocreatine; Rabbits

Topics: Adenine Nucleotides; Animals; Coronary Disease; Energy Metabolism; Heart; Heart Rate; Isoproterenol; Kinetics; Male; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains; Timolol

The ischemic state of the myocardium of the isolated working rat heart after induction of normothermic ischemic cardiac arrest was assessed by the interrelationship among changes in myocardial ultrastructure, mitochondrial oxidative phosphorylation, and tissue high energy phosphate contents. At all time intervals (10-40 minutes) studied, the ultrastructural changes were more severe in the subendocardium than in the subepicardium. After 25-40 minutes of normothermic ischemic cardiac arrest, the mitochondrial oxygen uptake (state 3) became increasingly depressed, particularly in mitochondria isolated from the subendocardium. Mitochondrial oxidative function, as measured in vitro, did not correlate well with mitochondrial ultrastructural damage. In addition, the effects of coronary reperfusion on the ability of the ischemic heart to recover in terms of ultrastructure, mechanical, and metabolic function were evaluated. Hearts subjected to 10-40 minutes of normothermic ischemic cardiac arrest showed almost complete ultrastructural recovery of the subepicardium upon reperfusion; regression of ultrastructural changes occurred to a lesser extent in the subendocardium. Reperfusion for 30 minutes did not alleviate the depression in mitochondrial oxidative function, while tissue ATP levels did not return to control, preischemic levels. After 20 minutes of normothermic ischemic cardiac arrest, the mechanical performance of the working heart during reperfusion was significantly depressed, compared with pre-ischemic control values. Normal ultrastructure of the subendocardium always accompanied mechanical recovery, while improvement of mitochondrial oxidative function was not essential.

Topics: Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Heart; Heart Arrest, Induced; Heart Rate; Male; Mitochondria, Heart; Myocardium; Oxidative Phosphorylation; Phosphocreatine; Rats; Rats, Inbred Strains; Stroke Volume

Using a modified Langendorff preparation, rabbit hearts were either continuously perfused at 37 degrees C for 150 min, in the presence of O2 and substrate, or after a 30 min equilibration period exposed to global ischemia followed by 30 min of reperfusion. Ischemia, for 90 min at 27 decrees C or for 60 min at 37 degrees C was compared. Perfusion pressure, heart rate, and ventricular volume were maintained constant. Contractile function and metabolic status were assessed. The effect of chlorpromazine, administered (30 mg/kg IP) 30 min prior to sacrifice, was compared to the untreated animal. (1) Chlorpromazine had little effect on the contractile function or metabolic status of hearts continuously perfused for 150 min in the presence of O2 and substrate. (2) The chloropromazine-treated hearts maintained contractile function and metabolic status at preischemic levels following exposure to 90 min of global ischemia at 27 degrees C and reperfusion at 37 degrees C. Untreated hearts exhibited a severe deterioration in both contractile and metabolic parameters under the same conditions. Both untreated and chlorpromazine-treated hearts exhibited loss of contractile function after 60 min ischemia at 37 degrees C; untreated hearts had undetectable ATP levels while chlorpromazine-treated hearts exhibited low levels of ATP. (3) Untreated hearts, exposed to 90 min of ischemia at 27 degrees C, exhibited a significant loss in compliance, while the compliance of chlorpromazine-treated hearts was unchanged from pre-ischemic levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Chlorpromazine; Compliance; Coronary Circulation; Coronary Disease; Female; Heart; Male; Myocardial Contraction; Myocardium; Perfusion; Phosphocreatine; Rabbits

An isolated working rat heart preparation was used to determine the effect of diltiazem, a calcium antagonist, on the myocardial metabolism and functional recovery in the ischemic and reperfused heart, under conditions of 15 degrees C of topical hypothermia. The hearts were divided into two groups according to the solution injected into aortic root at the onset of ischemia. Group I (25 hearts) were given 3 ml of cold Krebs-Henseleit bicarbonate buffer solution (KHB), and Group II (25 hearts) were given the same dose of KHB containing 300 micrograms of diltiazem. After 30 min of reperfusion following 120 min of ischemia, cardiac output (ml/min) was significantly better in Group II (24.1 +/- 3.2) than in Group I (9.5 +/- 2.5). There were no differences between the groups with regard to tissue levels of creatine phosphate, adenosine triphosphate (ATP), total adenine nucleotide (TAN), glucose-6-phosphate and lactate during the ischemia. However, ATP and TAN levels were significantly higher in Group II after 30 min of reperfusion. These data show that, although diltiazem has little effect in preventing the catabolism of high-energy phosphates during hypothermic ischemia, there was an improvement in myocardial metabolism and an enhanced functional recovery during reperfusion in the diltiazem-treated hearts.

Topics: Adenine Nucleotides; Animals; Benzazepines; Coronary Circulation; Coronary Disease; Diltiazem; Glucosephosphates; Heart; Hemodynamics; Hypothermia, Induced; Lactates; Male; Myocardium; Perfusion; Phosphocreatine; Rats; Rats, Inbred Strains; Time Factors

The recovery of high energy phosphate compounds in perfused guinea-pig heart at 20 degrees C after a 12 min period of global ischaemia was examined using 31P-NMR with a time resolution of 12 s. This time resolution was achieved by overlaying the data acquired from five successive ischaemic periods by arresting and restoring the flow of perfusion fluid to the heart in synchrony with the data acquisition sequence. The rate of creatine phosphate resynthesis after the ischaemic period proceeded 14 times faster than its rate of loss during the ischaemic period. ATP levels did not decrease during ischaemia and ADP was undetectable at any time. Estimates of intracellular pH from the chemical shift of the inorganic phosphate peak were impossible in normal guinea-pigs since the inorganic phosphate peak was not clearly defined. During the ischaemic period the inorganic phosphate peak increased in size and shifted upfield. On restoration of flow, the inorganic phosphate peak collapsed in a complex way following a different path to its formation during ischaemia.

Topics: Acid-Base Equilibrium; Adenosine Diphosphate; Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Guinea Pigs; Hydrogen-Ion Concentration; Intracellular Fluid; Magnetic Resonance Spectroscopy; Male; Phosphates; Phosphocreatine; Sugar Phosphates

The role of ventricular filling pressure (VFP) as a determinant of coronary blood flow (CBF) in the acutely ischemic ventricle was examined in the open-chest dog under conditions of a reduced, constant coronary artery pressure and an unstable VFP. Blood delivery to different layers of the ventricle and ischemic metabolic changes occurring in these layers were also determined and compared with appropriate control data. A close, inverse, linear relationship between VFP and CBF was found in animals exhibiting a progressive rise in VFP from 6 +/- 0 to 25 +/- 1 mmHg (r = 0.99). A lower endocardial-to-epicardial ratio of delivered blood and a steeper transmural gradient in ischemic metabolic changes were noted in these animals compared with similarly prepared animals exhibiting a stable VFP. The findings demonstrate the importance of VFP as a determinant of CBF during ischemia, and they lend support to the concept that blood flow in the ischemic ventricle is regulated by a preload-dependent transmural gradient in coronary driving pressure.

Topics: Animals; Blood Pressure; Coronary Circulation; Coronary Disease; Dogs; Heart Ventricles; Lactates; Lactic Acid; Perfusion; Phosphates; Phosphocreatine

Topics: Adenosine Triphosphate; Animals; Arterial Occlusive Diseases; Coronary Circulation; Coronary Disease; Dogs; Hemodynamics; Myocardial Contraction; Myocardial Infarction; Myocardium; Necrosis; Perfusion; Phosphocreatine; Time Factors

The enhancement of ATP regeneration following global myocardial ischemia in dogs by both ATP catabolic enzyme blockade and precursor infusion was investigated. The breakdown of AMP to adenosine is catalyzed by 5'-nucleotidase and this enzyme was inhibited during the ischemic period with either concanavalin A (Con A, 3 mg/kg) or alpha, beta-methyleneadenosine 5'-diphosphate (AMP-CP, 250 microM). To provide additional ATP precursors, adenine (30 mg/kg) and ribose (25 mg/kg) (A/R) were also infused into the coronary vasculature during ischemia and recovery on cardiopulmonary bypass. Left ventricular myocardial ATP levels in control animals decreased to 52% of preischemic values during aortic cross clamping, but ATP levels in dogs treated with AMP-CP + A/R fell to only 67% of preischemic values (P less than 0.05). During reperfusion, ATP levels in Con A + A/R (3.43 +/- 0.26 mumol/g wet wt) and AMP-CP + A/R (3.77 +/- 0.42) treated animals were higher than values found in control dogs (2.73 +/- 0.16, P less than 0.05). Infusions of A/R alone without enzyme inhibition did not increase ATP regeneration. The adenine nucleotide energy charge ratio was also increased by enzyme blockade with either inhibitor when combined with precursor infusion. On bypass, left ventricular myocardial blood flow (measured by the microsphere technique) was increased by 140% (P less than 0.01) over control values in all groups receiving A/R; therefore, enhanced ATP levels were not merely the result of increased flow. Renal blood flow was not adversely affected by this combination of drugs as has been previously found with adenosine infusion and inhibition of adenosine catabolism.

Topics: Adenosine; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Blood Flow Velocity; Coronary Disease; Dogs; Energy Metabolism; Myocardium; Phosphocreatine; Renal Circulation

The extent of cardiac myosin light chain phosphorylation was measured during regional myocardial ischemia in the dog. A multiple-projectile cutter was used to sample adjacent biopsies from the normal and ischemic areas of the myocardium in an open-chested dog heart following 30 min of coronary artery ligation. Measurement of metabolite levels and blood flow in the individual biopsies clearly defined the border zone between normal and ischemic myocardium. Myosin light chain phosphorylation was measured after isoelectric focusing of biopsy samples and subsequent densitometric analysis. A 50% increase in phosphorylation was observed in the ischemic zone which may correlate with the reduced contractility which is a feature of the ischemic myocardium.

Topics: Animals; Biopsy; Coronary Disease; Dogs; Myocardium; Myosins; Phosphocreatine; Phosphorylation

The recovery of high energy phosphate stores (ATP plus phosphocreatine) was examined following various periods of reperfusion after 20 min circumflex artery occlusion in the open-chest dog. Transmural tissue samples were obtained from the posterior wall of the left ventricle of control dogs, after 20 min occlusion and after 1, 5, 10, 15 and 20 min reperfusion. Significant reductions in high energy phosphate stores were observed in the subepicardium (41.6% of control) and subendocardium (31.3% of control) after occlusion. Upon reperfusion, recovery was rapid and exceeded control by 65.4% (91.0 v. 55.0 microns/g dry wt) in the subendocardium, but only by 2.6% (72.2 v. 70.4, mumg/g dry wt) in the subepicardium and was due mainly to recovery of phosphocreatine. Regional myocardial blood flow was studied in a separate, but identical, series of experiments. During occlusion, posterior wall blood flow was reduced by 54% (0.85 +/- 0.04 to 0.37 +/- 0.04, ml/g/min) in the subepicardium and by 94.7% (1.13 +/- 0.05 to 0.06 +/- 0.005, ml/g/min) in the subendocardium. Reperfusion produced a rapid recovery including overshoot of blood flow compared to control blood flow. Peak blood flow occurred one minute after release of the occlusion becoming 3.34 +/- 0.16 ml/g/min in the subepicardium and 2.39 +/- 0.13 ml/g/min in the subendocardium. Blood flow in both levels returned to control flow after 15 min reperfusion. These results indicate that metabolic recovery of high energy phosphate stores occurred within 5 min of restoration of blood flow in this model.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Arterial Occlusive Diseases; Coronary Circulation; Coronary Disease; Dogs; Endocardium; Glucose-6-Phosphate; Glucosephosphates; Heart Ventricles; Hyperemia; Myocardium; Phosphocreatine

Isolated rat hearts were subjected to 30 min low flow ischaemia (0.5 ml X min-1). During reperfusion, uridine (5 X 10(-5) mol X litre-1) was added to the perfusion medium for 30 min. The concentrations of creatine phosphate, adenine nucleotides, uridylic nucleotides and glycogen were determined at the end of the experiments. The purpose of this work was to study the effects of uridine supply on the concentration of energetic compounds during reperfusion recovery. Low flow ischaemia induced a breakdown of creatine phosphate, adenosine triphosphate, and total adenine nucleotides by 53%, 23% and 15% respectively. The creatine phosphate content was restored during reperfusion without uridine, but the adenine nucleotides remained unchanged. The uridylic nucleotides and the glycogen were also degraded during ischaemia by 56% and 53% for uridine triphosphate and glycogen respectively. Reperfusion without uridine induced a partial resynthetisation of uridylic nucleotides but glycogen stores were not significantly restored. When tested in oxygenated hearts, uridine supply induced a fall in creatine phosphate concentration and an enhancement of uridine triphosphate level but it had no effect on adenosine triphosphate, uridine diphosphate glucose or glycogen concentrations. If supplied during reperfusion, the nucleoside induced the complete restoration of myocardial ATP, total adenine nucleotide content, an increase in the uridylic nucleotide concentration and the resynthetisation of glycogen to supra-normal value.

Topics: Adenine Nucleotides; Animals; Coronary Disease; Female; Glycogen; Heart; Myocardium; Perfusion; Phosphocreatine; Rats; Rats, Inbred Strains; Uracil Nucleotides; Uridine

The mechanisms underlying protection of ischemic myocardium by reperfusion with solutions containing reduced concentrations of calcium (CA) were studied in isolated vascularly perfused rabbit interventricular septa at 37 degrees C. After 45 min of total ischemia adenosine triphosphate (ATP), and phosphocreatine (PC) contents fell to 6.8 +/- 0.82, and 12.4 +/- 2.0 micrometer/g dry tissue (dt) (+/- S.E.M.). After 5 min of reperfusion with 0.75 mM Ca these values had recovered significantly to 10.3 +/- 1.0, and 33.3 +/- 3.6, (micrometer/g dt), while reperfusion with 2.5 mM Ca produced 5.9 +/- 1.0 and 22.0 +/- 2.6 (micrometer/g dt). The significantly greater recovery of ATP and PC after 0.75 mM Ca reperfusion persisted after an additional 25 min of reperfusion with 2.5 mM Ca when compared to septa reperfused for the entire 30 min with 2.5 mM Ca. When mechanical work was reduced by cessation of stimulation during the first 5 min of reperfusion, ATP, PC and total creatine (TC) recovery were significantly improved in muscles exposed to 2.5 mM Ca but showed no additional improvement in muscles reperfused with 0.75 mM Ca. A further reduction to 100 micrometers Ca reperfusion in quiescent muscles did significantly improve ATP, PC and TC recovery. Quiescence achieved with 16.0 mM K impaired ATP, PC and TC recovery. This effect was reversed by 100 micrometers CA reperfusion. Measurements of mitochondrial oxygen consumption, respiratory control and ADP/O showed results parallel to the ATP, PC and TC determinations. Both mechanical work and CA itself influence mitochondrial respiration, ATP, PC and TC content after ischemia. As previously demonstrated for mechanical function, metabolic recovery can be improved by interventions limited to the first 5 min of reperfusion.

Topics: Adenosine Triphosphate; Animals; Calcium; Coronary Disease; Creatine; Electric Stimulation; Myocardial Contraction; Myocardium; Perfusion; Phosphocreatine; Potassium Chloride; Rabbits

Studies in animal models of myocardial ischemia and left ventricular hypertrophy have demonstrated a number of derangements in purine and pyrimidine nucleotide content of myocardium that are postulated to play a role in the pathogenesis of muscle dysfunction in these disorders. The present study examined myocardium of patients with coronary artery disease, left ventricular hypertrophy, or neither of these two abnormalities, to determine whether derangements in purine and pyrimidine nucleotide metabolism occur in humans. In patients with coronary artery disease, endocardial content of ATP, GTP, UTP, CTP, and creatine phosphate was reduced and ranged between 60% and 86% of the amount found in the epicardium. In patients without coronary artery disease or ventricular hypertrophy, endocardial content of these nucleotides was equal to or greater than that of epicardium. Endocardial and epicardial content of inosine was increased in patients with coronary artery disease, and after vein bypass grafting inosine content fell to the levels observed in myocardium of patients with normal coronary arteries. In patients with left ventricular hypertrophy, endocardial content of ATP, GTP, UTP, CTP, and creatine phosphate was also reduced and ranged between 64% and 88% of the epicardial content. In contrast to results obtained in patients without left ventricular hypertrophy, epicardial content of GTP, UTP, and CTP was increased by 131%, 123%, and 132% in hypertrophied myocardium. Thus the changes noted in myocardial nucleotide content in patients are similar to those noted in animal models of occlusive coronary disease and ventricular hypertrophy. These results suggest that the pathophysiological abnormalities in nucleotide metabolism noted in animal models also occur in human myocardium.

Topics: Adenine Nucleotides; Cardiomegaly; Coronary Disease; Guanosine Triphosphate; Humans; Myocardium; NAD; Nucleotides; Phosphocreatine; Pyrimidine Nucleotides

The effect of diltiazem on ischemic myocardial acidosis was studied in the canine heart whose left anterior descending coronary artery was partially occluded to reduce coronary flow to about one-third (partial occlusion). Myocardial pH was measured by use of a micro glass pH electrode. The pH decreased from 7.53 to 6.93 by partial occlusion and appeared to reach a steady state within 30 min. Saline or drugs were injected i.v. 30 min after partial occlusion. The decreased pH increased spontaneously by 34% of the total reduction of pH in the next 60 min after saline injection. Diltiazem (100 micrograms/kg) potentiated the increase in pH; the pH increased by 76% 60 min after the injection. Propranolol (1 mg/kg) also potentiated the increase in pH that had been decreased by partial occlusion. The relation between pH decrease and the tissue levels of metabolites was also studied. The reduction of myocardial pH from 7.5 to 6.8 was accompanied by a 2-fold increase in the tissue lactate content and by decreases in the ATP and creatine phosphate contents. There was a significant correlation between the hydrogen ion concentration calculated from the pH and each of the lactate, ATP and creatine phosphate contents. The present study indicates that diltiazem attenuates ischemic myocardial acidosis.

Topics: Adenosine Triphosphate; Animals; Benzazepines; Calcium Channel Blockers; Coronary Disease; Diltiazem; Dogs; Hydrogen-Ion Concentration; Ion Channels; Lactates; Lactic Acid; Myocardium; Phosphocreatine; Propranolol

Effects of nitroglycerin on hemodynamics and transmural distribution of myocardial metabolites were studied at 40% of control coronary perfusion pressure induced by acute coronary stenosis in the canine heart. At 40% of coronary perfusion pressure, high energy phosphate (ATP, creatine phosphate) contents significantly diminished in all layers, especially in the inner layer. A 0.3 micrograms/kg/min intracoronary infusion of nitroglycerin showed no direct effects on energy metabolism in the underperfused myocardium. A 3 micrograms/kg/min i.v. administration of the drug under fixed coronary constriction resulted in decrease in left ventricular peak systolic pressure and systemic blood pressure, and further decrease in coronary perfusion pressure and coronary blood flow. Left ventricular end diastolic pressure and ST-segment of the epicardial ECG were elevated. High-energy phosphate contents further decreased while inorganic phosphate and lactate showed an increase. Under these conditions, release of the constriction sufficient for retention of the coronary perfusion pressure at about 40 mm Hg resulted in significant improvement of the myocardial energy metabolism without a further increase in coronary blood flow. The results suggest that when the myocardium is underperfused due to undilatable stenotic vessels with maximum autoregulation of the regional flow, it may be dangerous to administer nitroglycerin in a dose sufficient to produce a large decrease in coronary perfusion pressure.

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Coronary Circulation; Coronary Disease; Dogs; Electrocardiography; Energy Metabolism; Homeostasis; Lactates; Lactic Acid; Myocardium; Nitroglycerin; Phosphocreatine

Topics: Adult; Coronary Disease; Exercise Test; Female; Heart Rate; Hemodynamics; Humans; Male; Middle Aged; Myocardial Contraction; Myocardium; Oxygen Consumption; Phosphocreatine; Systole

The effects of long-term administration of prenylamine gluconate were studied to define changes induced by chronic treatment that may alter the responses of the myocardium to ischaemic stress. Prenylamine gluconate was administered orally to rats (10 mg or 100 mg/kg per day) for 2 weeks. At the end of this period, hearts were excised for perfusion studies. In comparison with gluconate-treated controls, hearts from the group treated with the lower dose of prenylamine showed a significant reduction in basal cardiac function that was not apparent in the group treated with the higher dose of prenylamine. After a period (35 min) of ischaemia stress (reduced flow), a reduction in enzyme leakage and an increase in post-ischaemic functional recovery were observed in hearts from animals treated with the lower dose of prenylamine. In contrast, hearts from the group treated with the higher dose showed no significant improvement. However, chronic prenylamine therapy was shown to reduce in a dose-dependent manner the incidence of post-ischaemic arrhythmias. Thus, although the antiarrhythmic efficacy of long-term treatment with this agent appears to be proportional to the dosage, the ability of prenylamine to reduce ischaemic damage and promote functional recovery does not show a linear relationship with the drug dose.

Topics: Adenosine Triphosphate; Animals; Arrhythmias, Cardiac; Coronary Disease; Dose-Response Relationship, Drug; Glycogen; Heart; Heart Function Tests; Male; Myocardium; Perfusion; Phosphocreatine; Prenylamine; Rats; Rats, Inbred Strains

A study was undertaken to evaluate the effect of acute occlusion of a coronary artery during cardioplegic arrest on myocardial preservation and to elucidate the influence of reestablishment of flow versus continued occlusion during the phase of myocardial reperfusion. Coronary occlusion was simulated, and myocardial viability was determined by measuring tissue levels of adenosine triphosphate (ATP) and creatine phosphate (CP) in biopsies of the posterior left ventricular wall. Eighteen pigs were divided into three equal groups consisting of animals with (1) patent right coronary arteries during arrest and reperfusion, (2) occluded right coronary arteries during arrest and patent during reperfusion, and (3) occluded right coronary arteries during arrest and reperfusion. The results of ATP and CP measurements showed that while poorer protection was afforded during two-hour arrest when the coronary artery was occluded, the risk of damage was much greater during reperfusion. Failure to restore adequate blood flow by retention of occlusion caused a concurrent decrease in ATP and CP levels below prescribed limits of myocardial tolerance. When occlusion occurs in the clinical setting, impeding cardioplegia and reperfusion, the importance of revascularization is emphasized.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Coronary Vessels; Disease Models, Animal; Heart; Heart Arrest, Induced; Hypothermia, Induced; Ligation; Myocardium; Perfusion; Phosphocreatine; Swine

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Dogs; Female; Hemodynamics; Hydrogen-Ion Concentration; Lactates; Lactic Acid; Male; Myocardium; Oxygen Consumption; Pantetheine; Phosphocreatine; Sulfhydryl Compounds; Time Factors

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Cardiac Output; Cardiopulmonary Bypass; Catecholamines; Coronary Disease; Dobutamine; Dogs; Dopamine; Heart; Myocardium; Oxygen Consumption; Phosphocreatine; Renal Circulation

This study was designed to evaluate the effect of ischemia and reperfusion on myocardial mechanical function and high-energy phosphates in the neonate. All studies were performed utilizing the isolated arterially perfused septal preparation of newborn and adult rabbit hearts that were maintained at 27, 33, or 37 degrees C and paced at 90 beats/min. After mechanical function had been stabilized, 60 min of global ischemia was induced and was followed by 60 min of reperfusion. The muscle was kept in a humidified, warm, oxygen-poor atmosphere. During ischemia, developed tension (DT) and maximal rate of tension development (+dT/dtmax) declined at the same rate in the newborn and the adult, and the values at the end of ischemia were not significantly different from 0. The resting tension (RT) increased significantly in the two age groups during ischemia, but the increase in the newborn was significantly less than that in the adult. After 60 min of reperfusion, the recovery of +dT/dtmax in the newborn was significantly greater than that in the adult at each temperature. Tissue ATP content in the newborn was significantly greater than that in the adult, both at the end of ischemia and after reperfusion. Importantly, a significant correlation (r = 0.90) between the recovery of +dT/dtmax and tissue ATP content was found. These data indicate that 1) the newborn myocardium is more resistant to ischemia than the adult myocardium and 2) this resistance might be explained by less depletion of myocardial ATP levels during ischemia.

Topics: Adenosine Triphosphate; Animals; Animals, Newborn; Coronary Disease; Heart; Myocardial Contraction; Phosphocreatine; Rabbits; Time Factors

Topics: Adenine Nucleotides; Adenosine Triphosphate; Animals; Brain Chemistry; Coronary Disease; Creatine; Necrosis; Phosphocreatine; Rats; Rats, Inbred Strains; Stress, Physiological

The aim of this study was to determine the temperature for optimal myocardial preservation during cardioplegic arrest. In isolated canine hearts perfused by a support dog, functional and metabolic recovery was measured after cardioplegic arrest using the St. Thomas' Hospital solution. The temperature range, -2 degrees to 37 degrees C, was studied using a 2 hour arrest period. A 6 hour arrest period was used to enhance differences in the range 4 degrees to 20 degrees C. Cooling to -2 degrees C produced severe mitochondrial damage seen on electron microscopy and zero recovery of function. Reperfusion after 2 hours of arrest at 4 degrees or 15 degrees C was followed by complete functional and metabolic recovery. As the temperature during arrest was raised above 20 degrees C, recovery decreased markedly, culminating in ischemic contracture at 37 degrees C. The severe stress of 6 hours of arrest revealed further increases in protection conferred by stepwise cooling to 4 degrees C. In diseased hearts, long periods of ischemia are less well tolerated than in the normal hearts used in this study. Therefore, the additional protection conferred by cooling to 4 degrees C is of clinical importance. The conclusion is that during cardioplegic arrest, provided freezing is avoided, the lower the myocardial temperature, the better is the protection against ischemia.

Topics: Adenosine Triphosphate; Animals; Cold Temperature; Coronary Disease; Dogs; Heart; Heart Arrest, Induced; Hypothermia, Induced; Lactates; Mitochondria, Heart; Myocardium; Phosphocreatine

This study tests the hypothesis that warm induction of cardioplegia prior to prolonged maintenance by multidose infusions of cold blood cardioplegic solution would increase the tolerance of energy-depleted hearts to subsequent aortic clamping. Eighty percent depletion of subendocardial adenosine triphosphate (ATP) was produced in 30 dogs by 45 minutes of normothermic ischemia. This was followed either by unmodified blood reperfusion or 2 additional hours of aortic clamping with multidose cold blood cardioplegia. We compared a brief (5 minute) period of 37 degrees C cardioplegic induction to standard 4 degrees C blood cardioplegic induction to determine if warm induction would enhance metabolic and functional recovery. Warm cardioplegic induction resulted in more oxygen consumption than cold induction (16.9 versus 8.1 cc/100 gm), and lower levels of glucose-6-phosphate (G6P), suggesting better aerobic metabolism (0.97 versus 1.87 microM/gm wet weight). Prompt repletion of creatine phosphate (CP) occurred with warm and cold cardioplegic induction, although ATP levels levels remained low. Hearts undergoing ischemia and unmodified reperfusion consumed insufficient oxygen to meet basal metabolic needs during reperfusion (7 cc/100 gm below requirement) and recovered only 33% +/- 5% of control left ventricular performance. Better function occurred with cold cardioplegic induction (63% +/- 5%), and almost complete recovery (85% +/- 5%) occurred when warm induction of cardioplegia was used. We conclude that warm induction followed by prolonged cold multidose blood cardioplegic arrest enhances aerobic metabolism, results in normal left ventricular performance, and improves tolerance of aortic clamping in energy-depleted hearts.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Dogs; Heart Arrest, Induced; Myocardium; Oxygen; Phosphocreatine

Topics: Adenosine Triphosphate; Animals; Coenzymes; Coronary Disease; Dogs; Hemodynamics; Ligation; Perfusion; Phosphocreatine; Tissue Survival; Ubiquinone

Topics: Adenosine Triphosphate; Adult; Coronary Artery Bypass; Coronary Disease; Creatine Kinase; Glycogen; Hemodynamics; Humans; Hypothermia, Induced; Isoenzymes; Mitochondria, Heart; Myocardium; Necrosis; Phosphocreatine

Topics: Animals; Coronary Disease; Cyclic AMP; Dogs; Lactates; Myocardium; Phosphocreatine; Phosphorylase Kinase; Phosphorylases; Propranolol; Protein Kinases

The isolated rat heart with ligation of the left coronary artery was used to assess the role of the beta 1- adrenergic receptor-cyclic AMP mechanism in the genesis of vulnerability to ventricular fibrillation in early myocardial ischaemia. Coronary artery ligation was followed after 3 min by a reduction in ventricular fibrillation threshold which reached a minimum at 15 min. This was accompanied by reduction of ATP and phosphocreatine while cyclic AMP was significantly increased in ischaemic myocardium. The dl-, l- and d-isomers of propranolol attenuated the decrease in ventricular fibrillation threshold and the increase in ischaemic myocardial cyclic AMP, without altering the tissue depletion of ATP. Specific beta 1-adrenergic receptor antagonism with atenolol did not prevent either the increase of tissue cyclic AMP or the reduction in ventricular fibrillation threshold and high energy phosphates. These findings suggest that the mechanism whereby vulnerability to fibrillation is increased in very early myocardial ischaemia is linked to changes in cyclic AMP content of ischaemic myocardium and appears independent of depletion of myocardial high energy phosphates.

Topics: Adenosine Triphosphate; Animals; Atenolol; Coronary Disease; Cyclic AMP; Heart; Male; Myocardium; Phosphates; Phosphocreatine; Propanolamines; Propranolol; Rats; Rats, Inbred Strains; Stereoisomerism; Ventricular Fibrillation

In 16 patients undergoing elective coronary artery bypass, transmural biopsies were performed during bypass but before global ischemia. Subendocardial and subepicardial halves were separately assayed in each sampled tissue. Adenosine triphosphate (ATP) levels, total adenine nucleotide content (sigma Ad), and creatine phosphate (CP) content were significantly higher (p less than 0.005) in the subepicardium than the subendocardium in regions of the heart distal to major occlusions: 35.36 +/- 2.12 nmole/mg versus 28.7 +/- 1.7 (ATP), 42.24 +/- 2.04 versus 35.6 +/- 1.6 (sigma Ad), and 29.99 +/- 4.32 +/- versus 16.35 +/- 3.48 (CP). The opposite was true in two hearts with normal coronary arteries, in which high-energy phosphates tended to be higher in the subendocardium than the subepicardium. A transmural metabolic gradient therefore exists in regions of the myocardium distal to significant coronary occlusive disease. The subendocardium's relative depression in metabolic reserve cold determine its susceptibility to ischemic damage and influence techniques designed to preserve the heart during ischemia.

Topics: Adenine Nucleotides; Adenosine Triphosphate; Biopsy; Coronary Artery Bypass; Coronary Disease; Endocardium; Humans; Myocardium; Phosphates; Phosphocreatine

The purpose of this study was to determine whether or not the biochemical, functional, and ultrastructural abnormalities produced by brief temporary coronary occlusions (unassociated with necrosis) ever resolve and, if so, when they do. Anesthetized open-chest dogs were subjected to 15 min of coronary artery occlusion followed by 72 hr, 7 days, or 14 days of reperfusion. Serial in vivo myocardial biopsies were performed for measurement of ATP and for ultrastructural analysis. Regional function was evaluated by sonomicrometry. Mean (+/- SEM) myocardial ATP concentration was 36.6 +/- 1.2 nmol/mg of cardiac protein in nonischemic subendocardium and 18.9 +/- 1.5 in ischemic subendocardium after 15 min of ischemia. ATP remainede performed for measurement of ATP and for ultrastructural analysis. Regional function was evaluated by sonomicrometry. Mean (+/- SEM) myocardial ATP concentration was 36.6 +/- 1.2 nmol/mg of cardiac protein in nonischemic subendocardium and 18.9 +/- 1.5 in ischemic subendocardium after 15 min of ischemia. ATP remainede performed for measurement of ATP and for ultrastructural analysis. Regional function was evaluated by sonomicrometry. Mean (+/- SEM) myocardial ATP concentration was 36.6 +/- 1.2 nmol/mg of cardiac protein in nonischemic subendocardium and 18.9 +/- 1.5 in ischemic subendocardium after 15 min of ischemia. ATP remained depressed in the reperfused previously ischemic subendocardium at both 90 min (68% of nonischemic value) and 72 hr (78% of nonischemic value) but returned to normal at 7 days. Regional systolic function and cardiac ultrastructural abnormalities required 7 days for full recovery. Histologic and histochemical analysis did not reveal necrosis at any time. Therefore, biochemical, functional, and ultrastructural abnormalities induced by brief periods of transient coronary occlusion not associated with necrosis do resolve completely but the recovery period is prolonged.

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Coronary Disease; Dogs; Heart; Heart Rate; Kinetics; Microscopy, Electron; Myocardium; Necrosis; Perfusion; Phosphocreatine

Rates of synthesis and degradation of heart protein were measured during 30 or 60 min of myocardial ischemia and during the 30 or 60 min following these ischemic periods. During ischemia, rates of protein synthesis and degradation were reduced. Resumption of control rates of coronary flow after 30 min of ischemia resulted in complete restoration of creatine phosphate and partial recovery of ATP (75%), developed pressure (79%), and cardiac output (80%). After 60 min of ischemia, restoration of flow completely restored creatine phosphate but resulted in poor recovery of ATP (57%), developed pressure (26%), and cardiac output (63%). During the recovery phase, rates of protein synthesis and degradation of protein to free amino acids were the same as in hearts that had been perfused for a comparable period as working aerobic preparations. These findings were consistent with inhibition of an initial step in proteolysis during the period of ischemia followed by return to control rates of degradation when oxygen delivery and energy levels were restored.

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Cardiac Output; Coronary Disease; Heart; Male; Muscle Proteins; Myocardium; Phenylalanine; Phosphocreatine; Rats

Transmural left ventricular biopsies were studied from 28 patients undergoing cardiopulmonary bypass with anoxic cardiac arrest. The myocardium was protected by topical cooling (20 degrees C) (Group 1, 15 patients) or by cardioplegia with St. Thomas' solution (Group 2, 13 patients). Biopsies were taken at the start of bypass and 3 to 5 minutes after unclamping of the aorta. Mean cross-clamp time was not significantly different between the groups (50 minutes for Group 1 and 53 minutes for Group 2; p greater than 0.05). The ultrastructural changes induced by ischemia and subsequent reperfusion were almost exclusively related to the mitochondria. The degree of mitochondrial damage was evaluated by a semiquantitative analysis based on mitochondrial fine structure. The frequency of severe postischemic mitochondrial damage was significantly higher in Group 1 (20.1% versus 2.7% in Group 2; p less than 0.05). Biochemical analysis of the biopsies indicates that the myocardial concentration of creatine phosphate decreases by about 50% after topical cooling (p less than 0.05). With St. Thomas cardioplegia, no significant change in the tissue level of this high-energy phosphate takes place. The results show evidence of the superiority of the St. Thomas cardioplegia to topical cooling alone.

Topics: Adult; Aortic Valve; Coronary Disease; Heart Arrest, Induced; Heart Valve Prosthesis; Humans; Hypothermia, Induced; Mitochondria, Heart; Phosphocreatine

Nuclear magnetic resonance (NMR) is a non-invasive technique which, when using 31Phosphorus (as is usually the case), provides sequential determinations of the concentrations of high energy phosphate compounds and of intracellular pH in tissues subjected to electro-magnetic pulses. NMR can now be applied to the whole heart and makes it possible to record simultaneously biochemical and haemodynamic data. Referring to personal cases, the authors emphasize the value of NMR as a new device for evaluating myocardial preservation techniques during both ischaemia and reperfusion.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Humans; Hydrogen-Ion Concentration; Intraoperative Care; Magnetic Resonance Spectroscopy; Myocardial Contraction; Myocardium; Phosphocreatine; Phosphorus

A new nonrotating multiple biopsy device has been developed to allow the rapid, simultaneous and contiguous sampling of cardiac muscle in the large mammalian heart. Each cutter obtains 40 adjacent transmural left ventricular biopsy samples, each of 4 mm section. The epicardial 1.8 mm of each biopsy section was analyzed for flow, adenosine triphosphate, adenosine diphosphate, adenosine monophosphate, creatine phosphate and lactate. Use of this procedure in the dog heart 30 minutes after coronary arterial ligation permitted characterization of the nature of flow and metabolic gradients as the sampling site moved from the core of an areas of regional ischemia to the surrounding normal tissue. These studies of metabolic and flow geometry in the lateral plane indicate the existence of a sharp interface of flow and metabolism between normal and ischemic tissue. The absence of intermediate levels of flow and metabolism indicate that, in the lateral plane at least, a quantitatively significant and spatially identifiable "border zone" region does not exist. However, these findings, do not preclude the existence of such a zone of jeopardized tissue in the transmural plane or the occurrence of a temporal border zone to which interfaces of flow and metabolism may migrate with time.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Dogs; Lactates; Myocardial Infarction; Myocardium; Phosphocreatine

Topics: Acute Disease; Adenosine Triphosphate; Animals; Coronary Disease; Glycogen; Lactates; Myocardium; Osmolar Concentration; Perfusion; Phosphocreatine; Potassium; Sodium; Swine; Water

The protective effects of diltiazem, a calcium channel blocker, were studied in isolated, blood-perfused cat hearts subjected to 60 or 90 min of global ischemia, followed by reperfusion of 60 or 120 min, respectively. Ischemia-induced alterations of left ventricular (LV) developed pressure (DP) and compliance, measured with an intraventricular fluid-filled latex balloon, were correlated with respiratory activity in vitro of mitochondria isolated from ischemic-reperfused LV myocardium. Nontreated isolated hearts sustained severe declines of LVDP as a result of 60 (-50 +/- 8%) and 90 min (-83 +/- 7%) of ischemia, whereas diltiazem-treated hearts demonstrated only minor losses of LVDP (-17 +/- 8 and -26 +/- 2%). Diltiazem prevented losses of compliance caused by 60 or 90 min of ischemia, which were severe in nontreated hearts after the latter period of ischemia. The progressive deterioration of mechanical function observed in nontreated hearts was paralleled by depressed mitochondrial oxygen consumption and respiratory control. The respiratory activity of mitochondria isolated from cat heart mitochondria. Diltiazem also prevented significant elevations of tissue and mitochondria Ca++ content, reflecting inhibition of Ca++ influx during ischemia and reperfusion. Also, recovery of ATP levels was greater after 60 min each of ischemia and reperfusion in diltiazem-treated hearts. Thus, diltiazem exerts direct, cardioprotective effects during myocardial ischemia, presumably by inhibiting transmembrane Ca++ fluxes.

Topics: Adenosine Triphosphate; Animals; Benzazepines; Body Water; Calcium; Cats; Compliance; Coronary Circulation; Coronary Disease; Diltiazem; Female; Lactates; Male; Mitochondria, Heart; Myocardial Contraction; Oxygen Consumption; Phosphocreatine; Pressure

Topics: Adenosine Triphosphate; Animals; Benzazepines; Blood Pressure; Coronary Disease; Diltiazem; Guinea Pigs; Heart; Heart Rate; In Vitro Techniques; Male; Myocardial Contraction; Perfusion; Phosphocreatine; Pyruvate Dehydrogenase Complex

(1) The recovery of perfused rat hearts experiencing various lengths of total global ischaemia was studied using 31P-NMR. Mechanical function was monitored by measuring left ventricular pressure. (2) Hearts exposed to a maximum of 14 min total global ischaemia regained stable contractile function on reperfusion. The concentration of phosphocreatine in these hearts rapidly exceeded its pre-ischaemic value while that of ATP rose very slowly. Pi fell on reflow to approximately its original level. These observations are interpreted as being the result of a rapid turnover of ATP stimulating phosphocreatine production by the mitochondrial isozyme of creatine kinase (ATP: creatine N-phosphotransferase, EC 2.7.3.2). (3) The recovery of intracellular pH on reperfusion does not depend upon the duration of ischaemia, nor on the pH or the percentage of ATP depletion at the end of the ischaemic period. This indicates that pH recovery is a flow-dependent phenomenon. (4) In non-recovering hearts, multiple Pi resonances are observed which arise from areas of differing myocardial pH. Phosphocreatine levels did not rise above 50% of their pre-ischaemic values. ATP levels remained depressed. This suggests that localized tissue necrosis only characterizes the failing situation.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Heart; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Male; Myocardial Contraction; Phosphocreatine; Rats; Rats, Inbred Strains

In this study we have assessed the possibility that long-term beta-blockade may offer additional protection against myocardial ischaemia that is separate from that afforded by acute beta-blockade. In addition, the effect of intrinsic sympathomimetic activity (ISA) on this additional protection was also investigated. Equipotent doses (4 mg . kg-1 body wt . day-1) of oxprenolol (possessing ISA) or propranolol (without ISA) were administered orally to rats for 3 weeks. Hearts were excised an perfused as isolated "working" heart preparations at variable times after the last dose. Hearts excised on the final day of drug administration showed significantly higher basal functional performance compared with untreated hearts. After 30 min reduced flow ischaemia (in the presence of exogenous catecholamine drive) hearts were aerobically reperfused and functional recovery measured. In both chronically beta-blocked groups, at times when plasma drug levels were undetectable, the number of hearts that recovered function and the cellular levels of creatine phosphate and glycogen were significantly increased. In addition, hearts from the oxprenolol-treated group perfused on the final day of drug administration, exhibited a greater recovery of heart rate compared with both propranolol treated and untreated groups. These results indicate that secondary consequences of long-term beta-blockade are beneficial to the ischaemic myocardium in the presence of high catecholamine drive. In addition, the possession of ISA by oxprenolol offered some advantages in terms of post-ischaemic functional recovery.

Topics: Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Glycogen; Hemodynamics; In Vitro Techniques; Male; Oxprenolol; Phosphocreatine; Propranolol; Rats; Rats, Inbred Strains

Fructose 1,6-diphosphate (FdP) reportedly protects ischemic myocardium. To determine whether this is a direct action on the heart, we used a canine model in which two coronary arteries were perfused at identical but reduced rates. Into one artery we infused FdP (total doses of 400 mg or 1.8 g) while the other received 0.9% NaCl. After 1 h, biopsies were taken from a normal region and the two ischemic regions and were analyzed for ATP, phosphocreatine (PC), and lactate content. In the 0.9% NaCl-treated ischemic tissue, ATP and PC fell to half the nonischemic levels. The FdP-treated tissue exhibited high-energy phosphate levels similar to the 0.9% NaCl-treated tissue with no significant differences between the two ischemic areas. Lactate levels in both ischemic areas were elevated threefold above nonischemic levels. Contractility studies showed that infusion of FdP directly into the coronary artery depressed contractility in both nonischemic and ischemic conditions. Our data show that, if FdP does have a protective action in ischemia, it is not through a direct action on the heart.

Topics: Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Dogs; Female; Fructosediphosphates; Hexosediphosphates; Lactates; Male; Myocardial Contraction; Myocardium; Phosphocreatine; Regional Blood Flow

The purpose of this study was to determine if biochemical, functional, and ultrastructural abnormalities persist in nonnecrotic postischemic myocardium salvaged by coronary reperfusion. Anesthetized dogs were subjected to 15 min of occlusion of the left anterior descending (LAD) coronary artery followed by 3 days of reperfusion. Biopsies were obtained for measurement of adenosine 5'-triphosphate (ATP) and creatine phosphate (CP) nmol/mg protein), and regional function was evaluated using sonomicrometry. Myocardial ATP concentration after 15 min of occlusion was 37 +/- 1 nmol/mg cardiac protein in nonischemic subendocardium and 19 +/- 2 nmol/mg in ischemic subendocardium. After the hearts underwent 90 min and 72 h of reperfusion, ATP remained significantly depressed in reperfused subendocardium with values of 25 +/- 5 and 29 +/- 2 nmol/mg, respectively (P less than 0.05 and P less than 0.01 compared with the nonischemic zone in which ATP remained normal). CP levels fell during ischemia but returned to normal by 90 min of reperfusion. Percent systolic shortening of myocardial segments fell from +18 +/- 1% (active shortening) to -13 +/- 2% (passive lengthening) during ischemia and was still significantly depressed at +11 +/- 1% (P less than 0.05 vs. preocclusion) at 72 h of reperfusion. Histological examination showed no necrosis, but ultrastructural abnormalities were present. Therefore brief periods of myocardial ischemia are not associated with necrosis but result in functional, biochemical, and ultrastructural abnormalities, which are present for at lest 3 days after coronary reperfusion.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Dogs; Microscopy, Electron; Myocardium; Perfusion; Phosphocreatine; Time Factors

High-energy phosphate content and mitochondrial function were analyzed at the initiation and completion of ischemic contracture in dog hearts exposed to normothermic ischemia while on cardiopulmonary bypass. Contracture initiation and completion were detected by a balloon catheter placed within the left ventricle. In seven dogs, inner and outer layers of the myocardium were assayed for adenosine triphosphate (ATP) and creatine phosphate (CP). ATP and CP content in these two layers were compared prior to ischemia and at contracture initiation and completion. Inner layer ATP levels were 23.88 +/- 0.73 (mean +/- SM) mu moles/gm dry weight prior to ischemia, 5.14 +/- 0.49 at initiation, and 0.73 +/- 0.2 at completion. Inner layer CP content was 41.29 +/- 0.87 prior to ischemia, 3.49 +/- 0.34 at initiation, and 4.06 +/- 0.48 at completion. Mitochondrial respiratory control indices (RCI) were assayed in a second group of seven dogs prior to ischemia, at contracture initiation, and at contracture completion and were, respectively, 11.5 +/- 1.18, 3.1 +/- 0.43 and 1.76 +/- 0.29 (alpha ketoglutarate as substrate). Despite the specific degrees of metabolic deterioration associated with the events of contracture, ischemic time required to develop contracture initiation and completion was variable, ranging from 29.5 to 72 minutes for initiation and 60.25 to 101 minutes for completion. A third group of five dogs had biopsy specimens taken for ATP at fixed ischemic time intervals, and at 45 minutes of ischemia they were found to have greater ranges in ATP values than the ranges associated with contracture initiation. In contrast to ischemic time, the physiological events of ischemic contracture are reliable predictors of the degree of metabolic injury in the intact dog heart exposed to normothermic ischemic arrest during cardiopulmonary bypass.

Topics: Adenosine Triphosphate; Animals; Cardiopulmonary Bypass; Coronary Disease; Dogs; Female; Male; Mitochondria, Heart; Myocardial Contraction; Myocardium; Oxygen Consumption; Phosphocreatine; Time Factors

Topics: Acetates; Action Potentials; Adenine Nucleotides; Animals; Caprylates; Coronary Disease; Fatty Acids, Nonesterified; Glycogen; Guinea Pigs; Heart; Humans; Linoleic Acids; Palmitic Acids; Phosphocreatine

Topics: Adenosine Triphosphate; Anaerobiosis; Animals; Buffers; Coronary Disease; Glycolysis; Hydrogen-Ion Concentration; Lactates; Myocardium; Phosphates; Phosphocreatine

31P nuclear magnetic resonance (NMR) spectroscopy was used to ascertain whether propranolol could reduce the development of myocardial acidosis during periods of ischaemic arrest and were studied. Cardiac pH progressively declined during ischaemia from a normal 6.97 +/- 0.02 (n = 23) to 6.09 +/- 0.04 or 5.96 +/- 0.04, respectively. Normalisation of pH following reperfusion occurred only in the 35 min ischaemic hearts. Propranolol (1 mg. litre-1) given prior to arrest significantly reduced the magnitude of developing acidosis regardless of the length of ischaemia. Furthermore, it aided in the normalisation of intramyocardial pH upon reperfusion in both groups. Propranolol significantly reduced the magnitude of phosphocreatine (PCr loss normally seen during ischaemic arrest alone, but it did not protect against depletion of ATP. Restoration of PCr reperfusion was virtually complete in all cases, while transient increases in ATP were seen only in those hearts protected by propranolol. In summary, this NMR study demonstrated the first direct evidence that a significant component of the myocardial acidosis caused by global ischaemia and arrest can be blocked by propranolol.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Guinea Pigs; Heart; Hydrogen-Ion Concentration; In Vitro Techniques; Magnetic Resonance Spectroscopy; Male; Myocardium; Perfusion; Phosphocreatine; Phosphorus; Propranolol

Topics: Coronary Disease; Energy Metabolism; Energy Transfer; Humans; Myocardial Contraction; Myocardium; Phosphocreatine

Structural and functional changes in the mitochondrium have been described following timed cardiac ischemia. However, mitochondrial abnormalities associated with acute muscular dysfunction have not been well defined. In the present investigation, the isolated rat heart subjected to global ischemia was used to determine the relationship between the biochemical parameters of high-energy phosphate content and mitochondrial function and the physiological event of ischemic contracture. High-energy phosphate content and mitochondrial structure and function were determined under control conditions, at the initiation of ischemic contracture, at the completion of ischemic contracture, and 20 minutes after completion of contracture. Contracture initiation and completion were associated with the anticipated depletion of high-energy phosphate content. Also demonstrated were specific degrees of structural and functional deterioration of the mitochondria associated with specific degrees of contracture. In addition to its prior applications, this model seems well suited for investigation of the interdependence of high-energy phosphate levels, ischemic contracture, and mitochondrial function as affected by specific protective interventions designed to limit ischemic injury.

Topics: Adenosine Triphosphate; Animals; Contracture; Coronary Disease; Male; Mitochondria, Heart; Phosphocreatine; Rats

Topics: Adenosine Triphosphate; Aerobiosis; Animals; Calcium; Coronary Disease; Male; Mitochondria, Heart; Nifedipine; Oxidative Phosphorylation; Perfusion; Phosphocreatine; Propranolol; Pyridines; Rabbits; Systole; Verapamil

A study has been made of the simultaneous evolution of cardiac activity and metabolism in the dog heart in situ, during the perfusion of isoproterenol in a dose comparable to therapeutic doses (1 micrograms x kg-1 x min-1, 30 min). A total cardiopulmonary by-pass system allowed of taking the repeated myocardial tissue samples necessary for the determination of the main energetic substrate and high-energy phosphate content. Samples were taken from subendocardial and subepicardial layers separately. The acceleration of heart rate due to isoproterenol was quickly regressive but, in the well-irrigated heart, the drug elicited a rapid fall in glycogen content and a considerable rise in lactate content, a slower reduction in free fatty acid concentration restricted to the subendocardial layer, and no significant variation of creatine phosphate or ATP. In the ischemic heart, isoproterenol aggravated the glycolysis disturbances without completely losing its effects on lipolysis when the ischemia was not too marked.

Topics: Adenosine Triphosphate; Animals; Cardiopulmonary Bypass; Coronary Disease; Dogs; Fatty Acids, Nonesterified; Female; Glucose; Glycogen; Heart; Heart Rate; Isoproterenol; Lactates; Male; Myocardium; Phosphocreatine

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Coronary Vessels; Diastole; Edema, Cardiac; Elasticity; Heart Ventricles; Lactates; Male; Myocardial Contraction; Myocardium; Phosphocreatine; Pressure; Rabbits; Time Factors

Cardiac muscle biopsy specimens were obtained from 33 patients undergoing open-heart surgery under K+-induced ischemic arrest in hypothermia (cardioplegic right atrial and right ventricular muscles) or under hypothermic ischemic arrest without K+-cardioplegia (noncardioplegia right atrial muscle), and sequential patterns of changes in the myocardial metabolism were studied by standard enzymatic techniques. The concentrations of the high energy phosphates were not only adequately preserved but actually exceeded the initial values in the cardioplegic muscles during the 40-min period of the ischemic arrest. In addition, elevated ammonia levels were neutralized by these muscles, and excessive variations in the myocardial intermediary metabolism were prevented. The levels of ATP were also adequately preserved by the noncardioplegic right atrial muscle during the 12-min period of ischemic arrest. But this protection was achieved at the expense of a 20% reduction in the myocardial creatine phosphate levels and other associated severe intracellular metabolic derangements. Changes in the myocardial intermediary metabolism, at the end of 12 min of ischemic arrest and at the end of 40 min of K+-cardioplegic arrest, were almost identical. The results of these studies suggest that, in contrast to the hypothermic arrest alone, K+-cardioplegia in hypothermia offers a superior myocardial metabolic preservation over an extended period of time.

Topics: Ammonia; Cardiac Surgical Procedures; Coronary Disease; Heart; Heart Arrest, Induced; Humans; Hypothermia, Induced; Myocardium; Organophosphorus Compounds; Phosphocreatine; Potassium

The hemodynamic, electrocardiographic, and metabolic responses of dogs with acute myocardial ischemia to intravenous administration of fructose-1,6-diphosphate (FDP) were assessed. Analysis of the results (compared to dextrose control) revealed evidence of major improvement of LVEDP and cardiac output, significant decrease of the ST segment, and large increases of ATP and CP in the ischemic district and to a lesser degree in the normally perfused myocardium. These results indicate that FDP intervenes in the Embden-Meyerhof pathway not only as a high energy substrate but also as a metabolic regulator influencing the activity of phosphofructokinase and that of pyruvate kinase. FDP also stimulates glycolysis in dog erythrocytes and increases their ATP and 2-3 DPG content by a factor of 2. The most significant finding in these studies is that this biochemical intervention appears to restore the depressed activity of glycolysis in ischemic myocardium.

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Cardiac Output; Coronary Disease; Dogs; Electrocardiography; Fructosediphosphates; Hemodynamics; Hexosediphosphates; Histocytochemistry; Lactates; Myocardium; Phosphocreatine

Topics: Adenosine Triphosphate; Aerobiosis; Albumins; Animals; Capillary Permeability; Coronary Circulation; Coronary Disease; Extracellular Space; In Vitro Techniques; Intracellular Fluid; Kinetics; Male; Myocardium; Perfusion; Phosphocreatine; Rats; Sorbitol

Topics: Adenosine Triphosphate; Animals; Cattle; Coronary Disease; Glyceraldehyde-3-Phosphate Dehydrogenases; Glycolysis; Hydrogen-Ion Concentration; Lactates; Myocardium; NAD; Phosphates; Phosphocreatine; Rats

1. Phosphorus-nuclear-magnetic-resonance measurements were made on perfused rat hearts at 37 degrees C. 2. With the improved sensitivity obtained by using a wide-bore 4.3 T superconducting magnet, spectra could be recorded in 1 min. 3. The concentrations of ATP, phosphocreatine and Pi and, from the position of the Pi resonance, the intracellular pH (pHi) were measured under a variety of conditions. 4. In a normal perfused heart pHi = 7.05 +/- 0.02 (mean +/- S.E.M. for seven hearts). 5. During global ischaemia pHi drops to 6.2 +/- 0.06 (mean +/- S.E.M.) in 13 min in a pseudoexponential decay with a rate constant of 0.25 min-1. 6. The relation between glycogen content and acidosis in ischaemia is studied in glycogen-depleted hearts. 7. Perfusion of hearts with a buffer containing 100 mM-Hepes before ischaemia gives a significant protective effect on the ischaemic myocardium. Intracellular pH and ATP and phosphocreatine concentrations decline more slowly under these conditions and metabolic recovery is observed on reperfusion after 30min of ischaemia at 37 degrees C. 8. The relation between acidosis and the export of protons is discussed and the significance of glycogenolysis in ischaemic acid production is evaluated.

Topics: Acidosis; Adenosine Triphosphate; Animals; Coronary Disease; Glycogen; Hydrogen-Ion Concentration; In Vitro Techniques; Intracellular Fluid; Kinetics; Magnetic Resonance Spectroscopy; Male; Myocardium; Perfusion; Phosphocreatine; Phosphorus; Rats

Restoration of blood flow after 15 or 45 min. of ischemia induced an immediate recovery of phosphocreatine level and adenylate energy charge whereas ATP and total adenine nucleotides remained significantly below their normal values. These results prove that oxidative phosphorylations are not impaired but that a pool of myocardial adenine nucleotides is lost during ischemia which cannot be restored shortly after reperfusion. The significance of energy charge as a regulatory parameter in the myocardium is discussed.

Topics: Adenine Nucleotides; Animals; Coronary Circulation; Coronary Disease; Dogs; Myocardium; Phosphocreatine; Time Factors

Topics: Adenosine Triphosphate; Animals; Arterial Occlusive Diseases; Coronary Disease; Electrophysiology; Glycogen; Heart; Histocytochemistry; Lactates; Membrane Potentials; Myocardium; Phosphocreatine; Swine; Time Factors

In line with studies on the metabolism of the ischemic myocardium, the effectiveness of diltiazem hydrochloride, a potent calcium antagonist, in reducing the effects of ischemia was evaluated. Nonischemic and ischemic tissue samples were examined in two groups of dogs--Group I, dogs receiving no drug and killed after 60 minutes of regional ischemia, and Group II, dogs given diltiazem after 10 minutes of ischemia and killed 50 minutes later. Administration of diltiazem proved beneficial in several ways: The decrease in adenosine-5'-triphosphate in the ischemic region was halved, inhibition of anaerobic glycolysis was reduced, tissue levels of lactic acid and free fatty acids were lowered and the contractility of glycerinated heart muscle fibers was improved. However, administration of the drug did not influence mitochondrial function. Mitochondrial oxygen consumption and respiratory control were reduced by equal amounts in both groups, as was mitochondrial calcium ion binding. These observations demonstrate that diltiazem is capable of minimizing the consequences of acute ischemic, although the beneficial effects do not extend to all aspects of myocardial metabolism.

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Animals; Benzazepines; Blood Pressure; Calcium; Coronary Disease; Diltiazem; Dogs; Drug Evaluation, Preclinical; Fatty Acids, Nonesterified; Glycolysis; Heart Rate; Lactates; Mitochondria, Heart; Myocardial Contraction; Myocardium; Oxygen Consumption; Phosphocreatine

The relationship between energy metabolism and the extent of irreversible ischemic damage was examined in an isolated perfused working rat heart. The amount of cardiac work recovered after reperfusion of hearts exposed to severe global ischemia was dependent upon both the duration of ischemia and the type of substrate provided (either 5 mM glucose or 5 mM glucose + acetate). There appear to be two distinct phases in the ability to recover mechanical function in the reperfused ischemic heart. The second phase corresponds to the onset of severe irreversible tissue damage. Irreversible mitochondrial damage was not found to correspond with the onset of heart failure since the ATP/ADP ratio remained constant in the reperfused myocardium. Furthermore, there does not appear to be a direct correlation between the total ATP content and the extent of irreversible damage, either during ischemia or following reperfusion. However, the total adenine nucleotide content during ischemia showed dramatic changes which correspond temporally with the initiation of the second phase of damage. The observation that the adenine nucleotide pool becomes further depleted during reperfusion suggests that alterations in the salvage pathway for adenine nucleotide synthesis have occurred. Loss of adenine nucleotides appears to be an excellent marker for irreversible heart failure. Acetate provides some protection the the ischemic myocardium. The mechanism by which acetate mediates this protective effect is discussed.

Topics: Adenine Nucleotides; Adenosine Diphosphate; Adenosine Triphosphate; Animals; Cardiac Output; Coronary Circulation; Coronary Disease; Glucose; Insulin; Male; Mitochondria, Heart; Myocardium; Phosphocreatine; Rats

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Coronary Disease; Dogs; Evaluation Studies as Topic; Heart Arrest, Induced; Hypothermia, Induced; Myocardium; Phosphocreatine; Potassium

FREE FATTY ACIDS (FFA) IN EXCESS FFA: albumin molar ratios have been determined to additionally compromise mechanical performance in ischemic hearts. Carnitine, an intracellular carrier of FFA and an agent which is lost to the heart during ischemia, has been postulated to in part restore function with its replacement. To test whether its benefits are also operative in a setting of excess FFA, these studies were performed. In the main protocol, four groups of perfused swine hearts (n = 45) were compared during 50 min of control flow (179.7 ml/min) and 40 min of global ischemia (106.1 ml/min). Initial base-line serum FFA:albumin molar ratios and carnitine levels in all groups were 1.3:1 and 8.5 nmol/ml, respectively. In two of these groups FFA:albumin ratios were increased to 5.9:1 with constant infusions of Intralipid. In two alternate groups (one with and one without extra FFA supplements) dl-carnitine was supplied, sufficient to increase serum levels nearly 200-fold. Ischemia per se in 14 hearts significantly decreased several parameters of global and regional mechanical function including left ventricular (LV) and mean aortic pressures, LV isovolumetric pressure development (max dp/dt), LV epicardial motion, and LV work, together with concomitant decreases in myocardial oxygen consumption. Elevated FFA in 12 hearts rendered similarly ischemic further decreased mechanical function (LV pressure: -20.8%, P < 0.05; mean aortic pressure -26.9%, P < 0.05; LV max dp/dt: -39%, P < 0.05; regional LV shortening: -51.1%, P < 0.05; and LV work: -50.3%, P < 0.05) as compared with nonsupplemented hearts. dl-Carnitine treatments in nine hearts, not supplemented with extra FFA were without apparent effect in improving overall hemodynamic performance. However, dl-carnitine in 10 high FFA-ischemic hearts effected several improvements as compared with the untreated group: LV pressure was increased 25.6%, P < 0.025; mean aortic pressure: +43.5%, P < 0.05; LV max dp/dt: +41.5%, P < 0.05; regional LV shortening: +241.3%, P < 0.001; and LV work: +76.2%, P < 0.05 at comparable levels of myocardial oxygen consumption. In a separate protocol, the effects of stereospecificity were also studied by comparing l- with dl-carnitine in globally perfused, palmitate-supplemented hearts (five hearts in each treatment group). At similar conditions of flow and serum FFA, changes in mechanical function were comparable, except for a tendency to perform greater LV work at reduced flows in the

Topics: Adenosine Triphosphate; Animals; Aorta; Blood Pressure; Carnitine; Coronary Circulation; Coronary Disease; Fatty Acids, Nonesterified; Heart Ventricles; Myocardium; Oxygen Consumption; Phosphocreatine; Pressure; Swine

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Disease Models, Animal; Dogs; Lactates; Microscopy, Electron; Myocardium; Phosphocreatine

31P nuclear magnetic resonance (NMR) studies of creatine phosphokinase (CPK) kinetics using saturation transfer techniques are reported. The phosphocreatine (PCr) and adenosine triphosphate (ATP) levels in perfused hearts can be altered experimentally by stopping the flow of perusate (ischemia) to the heart for 35-min periods, followed by reperfusion to produce stable levels of performance. Utilization of energy by the heart was altered by administration of 25 mM potassium chloride (KCl) in the perfusate, which arrests contraction of the myocardium. Compared with control heart studies, the unidirectional rates measured during ischemia and KCl arrest are altered. The rates observed in the control experiments indicate that the CPK system is not in a steady state. This apparent deviation from steady-state conditions is ascribed to the existence of intracellular compartmentation of ATP.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Creatine Kinase; Heart; Magnetic Resonance Spectroscopy; Muscles; Myocardium; Perfusion; Phosphocreatine; Potassium Chloride; Rabbits

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Dogs; Female; Inosine; Male; Myocardial Contraction; Phosphocreatine; Stimulation, Chemical; Vasodilation

The precise mechanism responsible for early contractile failure after the onset of myocardial anoxia or ischemia has attracted speculation and controversy. The simple and attractive hypothesis that adenosine triphosphate (ATP) deficiency is responsible for this failure has often been dismissed on the basis of claims that there is only a small reduction in cell ATP content at a time when contractile activity is severely reduced. The premise of this article is that the changes in cell ATP content and distribution that theoretically should occur after oxygen depletion may not have been adequately considered and that previous measurements of cell ATP content may not have been carried out at the correct time. Using an isolated rat heart preparation and high speed freeze-clamping techniques it has been possible to demonstrate that a substantial decrease in myocardial ATP and creatine phosphate content occurs after the onset of anoxia but before the onset of contractile failure. Thus, during the first 5 seconds of anoxia contractile activity remains constant whereas ATP decreases by 25 percent and creatine phosphate by 50 percent. Thereafter, contractile failure occurs and the rate of utilization of high energy phosphates declines with the cell content at a plateau or possibly increasing. These results are assessed in the light of the dynamic changes in energy metabolism occurring in early anoxia and suggest that ATP depletion in a specific cell compartment may be the primary trigger for early contractile failure.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Energy Metabolism; Hypoxia; Male; Myocardial Contraction; Myocardium; Phosphocreatine; Rats; Shock, Cardiogenic

Cold blood with potassium, 34 mEq/L, was compared with cold blood and with a cardioplegic solution. Three groups of 6 dogs had 2 hours of aortic cross-clamp while on total bypass at 28 degrees C with the left ventricle vented. An initial 5-minute coronary perfusion was followed by 2 minutes of perfusion every 15 minutes for the cardioplegic solution (8 degrees C) and every 30 minutes for 3 minutes with cold blood or cold blood with potassium (8 degrees C). Hearts receiving cold blood or cold blood with potassium had topical cardiac hypothermia with crushed ice. Peak systolic pressure, rate of rise of left ventricular pressure, maximum velocity of the contractile element, pressure volume curves, coronary flow, coronary flow distribution, and myocardial uptake of oxygen, lactate, and pyruvate were measured prior to ischemia and 30 minutes after restoration of coronary flow. Myocardial creatine phosphate (CP), adenosine triphosphate (ATP), and adenosine diphosphate (ADP) were determined at the end of ischemia and after recovery. Changes in coronary flow, coronary flow distribution, and myocardial uptake of oxygen and pyruvate were not significant. Peak systolic pressure and lactate uptake declined significantly for hearts perfused with cold blood but not those with cold blood with potassium. ATP and ADP were lowest in hearts perfused with cardioplegic solution, and CP and ATP did not return to control in any group. Heart water increased with the use of cold blood and cardioplegic solution. Myocardial protection with cold blood with potassium and topical hypothermia has some advantages over cold blood and cardioplegic solution.

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Animals; Blood; Cardiopulmonary Bypass; Cold Temperature; Coronary Disease; Dogs; Glycolysis; Heart Arrest, Induced; Heart Ventricles; Hemodynamics; Hypothermia, Induced; Myocardium; Perfusion; Phosphocreatine; Potassium

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Coronary Disease; Dogs; Female; Heart; Male; Myocardium; Perfusion; Phosphocreatine; Propranolol

Using experimental models of various disease states, the ability of the isolated perfused working rat heart to withstand and recover from a period of severe ischemia was investigated. The results revealed that the coexistence of a diabetic state, obesity, or left ventricular hypertrophy increased the susceptibility of the hearts to ischemic damage and reduced the rate or the extent of postischemic recovery. In contrast, hearts obtained from moderately hypertensive rats exhibited a greater resistance to, and a superior recovery from, ischemia than did hearts obtained from normotensive controls.

Topics: Adenosine Triphosphate; Animals; Cardiac Output; Cardiomegaly; Coronary Circulation; Coronary Disease; Diabetes Mellitus, Experimental; Disease Models, Animal; Electrolytes; Heart Arrest, Induced; Hypertension; Male; Myocardial Contraction; Myocardium; Obesity; Phosphocreatine; Procaine; Rats; Triglycerides

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Cyclic AMP; Dogs; Female; Haplorhini; Lactates; Male; Myocardium; Papio; Phosphocreatine; Ventricular Fibrillation

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Animals; Aorta; Cardiac Surgical Procedures; Cardiopulmonary Bypass; Coronary Disease; Depression, Chemical; Dogs; Humans; Myocardial Contraction; Perfusion; Phosphocreatine; Potassium

Topics: Acetylcarnitine; Acyl Coenzyme A; Adenosine Triphosphate; Animals; Carnitine; Coenzyme A; Coronary Disease; Dogs; Hypoxia; Lactates; Myocardium; Phosphocreatine; Rats

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Carnitine; Coronary Circulation; Coronary Disease; Dogs; Electrocardiography; Heart; Mitochondrial ADP, ATP Translocases; Myocardium; Phosphocreatine

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Coronary Disease; Dogs; Electric Stimulation; Heart; Heart Rate; Heart Ventricles; Lactates; Male; Oxygen Consumption; Phosphocreatine; Regional Blood Flow; Ventricular Function

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Creatine Kinase; Cytoplasm; Glycogen; Hypoxia; Injections, Subcutaneous; Male; Mitochondria, Heart; Myocardium; Oxygen Consumption; Phosphocreatine; Propranolol; Rabbits; Time Factors

Intracellular acidosis may depress myocardial function and metabolism during ischemia. In the present study, the function and metabolism of a globally ischemic, isovolumic cat left ventricle preparation, perfused with oxygenated Krebs-Ringer biocarbonate solution, was examined. Addition of tris(hydroxymethyl)-aminomethane (Tris) (15 mM) to the perfusate at physiologic pH and PCO2 increased performance during ischemia to a greater extent and for a longer period than low PCO2 )15 mmHg), alkalotic (pH, 7.8) perfusate and a control sucrose perfusate. Under nonischemic conditions the inotropic effect of Tris was only briefly greater than sucrose perfusate. The inotropic effect of Tris during ischemia did not appear to depend on changes in coronary flow, oxygen consumption, sodium concentration, perfusate osmolality, or catecholamine release. During ischemia, lactate production was unchanged with Tris, but increased with low PCO2-alkalosis. Tissue levels of ATP and creatine phosphate for control ischemic hearts did not differ from Tris-perfused or low PCO2-alkalosis hearts. Thus, Tris appears to exert an inotropic effect that is more prominent in ischemic than nonischemic myocardium. The results are consistent with the possibility that Tris acts as an intracellular buffer to increase the efficiency of energy production and/or utilization during ischemia.

Topics: Adenosine Triphosphate; Animals; Cats; Coronary Circulation; Coronary Disease; Lactates; Myocardial Contraction; Myocardium; Oxygen Consumption; Perfusion; Phosphocreatine; Sodium; Stimulation, Chemical; Tromethamine

Potassium-induced cardioplegia was studied in 38 mongrel dogs supported by normothermic cardiopulmonary bypass and subjected to 60 minutes of aortic cross clamping followed by 30 minutes of reperfusion. A study of preischemic and postischemic ventricular function and myocardial high-energy phosphate compounds, lactate, and glycogen showed substantial preservation of high-energy phosphates and ventricular performance when potassium cardioplegia was used. However, the substantial depression in contractility observed following ischemia nad reperfusion suggests that potassium cardioplegia alone does not provide adequate intraoperative protection of the myocardium.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Aorta; Cardiopulmonary Bypass; Constriction; Coronary Disease; Dogs; Glycogen; Heart Arrest, Induced; Lactates; Myocardial Contraction; Myocardium; Phosphocreatine; Potassium

Topics: Adenosine Triphosphate; Animals; Cardiac Surgical Procedures; Coronary Disease; Dogs; Evaluation Studies as Topic; Extracorporeal Circulation; Heart Arrest, Induced; Heart Valve Diseases; Heart Valve Prosthesis; Humans; Myocardial Contraction; Myocardial Revascularization; Myocardium; Phosphocreatine; Postoperative Complications

In open-chest dogs transient occlusion of the left anterior descending coronary artery induced an immediate decline in the creatine phosphate content of the ischaemic area, a lesser decline of the ATP and total adenine nucleotide contents and a rise in S-T segments. Reperfusion after 15 min restored creatine phosphate level and intramyocardial electrograms to normal whereas ATP and total adenine nucleotide levels stayed down. None of these parameters were modified in the nonischaemic area during the experiments. This study shows that there is no close relationship between electrical and biochemical events during either ischaemia or reflow.

Topics: Adenine Nucleotides; Adenosine Triphosphate; Animals; Coronary Disease; Dogs; Electrocardiography; Heart; Myocardium; Phosphates; Phosphocreatine; Time Factors

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Coronary Disease; Energy Metabolism; Heart Rate; Hydrogen-Ion Concentration; In Vitro Techniques; Magnetic Resonance Spectroscopy; Myocardial Contraction; Myocardium; Phosphates; Phosphocreatine; Rats

A computer technique for determination of the distribution of adenine nucleotides among compartmented, protonated, and metal-chelated species has been developed for the perfused rat heart. This procedure requires knowledge of tissue levels of creatine, creatine phosphate, ATP, ADP, and AMP and the glycolytic and respiration rates. The method is applicable to any physiological state of the organ and has been applied to transient behavior in aerobic, anoxic, and ischemic hearts. The results suggest that ADP uptake and ATP export by mitochondria are normally linked and equal in rate during aerobic metabolism or short-term anoxia but become separate and unequal during ischemia, so that mitochondrial adenine nucleotides, primarily AMP, accumulate.

Topics: Actins; Adenine Nucleotides; Animals; Computers; Coronary Disease; Creatine; Cytosol; Glucose; Hydrogen-Ion Concentration; Hypoxia; Insulin; Magnesium; Mitochondria, Muscle; Models, Biological; Myocardium; Perfusion; Phosphocreatine; Rats

Effects of coronary artery ligation on myocardial glycogenolysis were studied in the endo- and epicardial layers of the left ventricular wall in dogs pretreated with 10 or 100 microgram/kg (i.v.) of carteolol, a potent beta-adrenergic blocking agent. Coronary artery ligation was performed by ligating one of the small branches of the left anterior descending coronary artery. In control (saline-pretreated) dogs, an increase in phosphorylase alpha activity and an increase in breakdown of glycogen were observed in both endo- and epicardial layers after coronary artery ligation. In the presence of 10 or 100 microgram/kg of carteolol, however, increases in phosphorylase alpha activity and increase in breakdown of glycogen were not observed in either the endo or epicardial layers. These results indicate that pretreatment of the dog with carteolol inhibits the increase in glycogenolysis caused by coronary artery ligation. Nevertheless, carteolol did not completely inhibit the coronary artery ligation-induced increase in glucose-6-phosphate and lactate levels, and the coronary artery ligation-induced decrease in phosphocreatine level, particularly in the endocardial layers.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Coronary Vessels; Dogs; Female; Glucosephosphates; Glycogen; Heart Ventricles; Lactates; Levobunolol; Ligation; Male; Myocardium; Phosphocreatine; Phosphorylases

Disturbance of the microcirculation produced by the combined injection of the high molecular weight dextran and vasopressin led as soon as the first minutes (5 min) to the intensification of glycolysis. This was testified to by the reduction of glycogen concentration by 19.4 percent, elevation of the phosphorylase "A" activity by 30-36 percent and of the pyruvic acid by 36.9 percent. The ATP, ADP, AMP, and the KP concentration remained unchanged. The observed glycolysis changes can be regarded as the initial metabolic reactions resulting from hypoxia originating in microcirculation disturbances.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Chinchilla; Coronary Disease; Energy Metabolism; Glycogen; Lactates; Microcirculation; Myocardium; Phosphocreatine; Phosphorus; Phosphorylases; Pyruvates; Rabbits

During reperfusion, functional and metabolic recovery of the isolated working rat heart from one hour of ischemia was best in hearts selectively cooled at the onset of the ischemic interval by perfusion with 5 to 10 ml. of 10 degrees C. or 15 degrees C. Krebs-Henseleit buffer. Hearts similarly perfused at 4 degrees C., 20 degrees C. recovered significantly less well or not at all. Immediately after the hour of ischemia and prior to reperfusion, the absolute levels of glycogen and high-energy phosphates were best in the hearts perfused at 4 degrees C. However, metabolic function was best preserved in those perfused at 10 degrees C. and 15 degrees C., as evidenced by rapid recovery of high-energy phosphates and glycogen to control levels compared to metabolic deterioration in the 4 degrees C. group.

Topics: Adenosine Triphosphate; Animals; Cardiac Surgical Procedures; Coronary Disease; Glycogen; Hypothermia, Induced; Myocardium; Perfusion; Phosphocreatine; Rats; Time Factors

The effect of coronary artery ligation on myocardial glyocogenolysis was studied in the endo- and epicardial layers of the left ventricle in dogs pretreated with saline or 1 mg/kg of propranolol. Coronary artery ligation was performed by ligating one of the small branches of the left anterior descending coronary artery. Even after coronary artery ligation, neither increase in phosphorylase activity nor breakdown of glycogen was observed in both layers of ischemic region of myocardium in propranolol-pretreated dogs. These results indicate that pretreatment with propranolol inhibits the increase in glycogenolysis being caused by coronary artery ligation. Propranolol howefer, did not inhibit completely the coronary artery ligation-induced increase in glucose 6-phosphate and lactate and decrease in phosphocreatine in the myocardium, especially in the endocardial layers.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Coronary Vessels; Dogs; Endocardium; Female; Glucosephosphates; Glycogen; Lactates; Ligation; Male; Myocardium; Pericardium; Phosphocreatine; Phosphorylases; Propranolol

Topics: Adenosine Triphosphate; Animals; Aorta; Coronary Disease; Dogs; Heart Ventricles; Myocardium; Perfusion; Phosphocreatine

Topics: Adenosine Triphosphate; Animals; Atractyloside; Blood Pressure; Cardiac Output; Coronary Circulation; Coronary Disease; Dogs; Electrocardiography; Glycosides; Heart; Heart Rate; Lactates; Mitochondrial ADP, ATP Translocases; Myocardium; Phosphocreatine

The effects of atrial pacing on tissue metabolite levels known to be sensitive to ischemia were examined. Anesthetized dogs were thoracotomized and a pacing electrode was sutured to the right atrium. Pacing at rates of 200 or 250 beats/min (10 animals per group) was performed for 15 min after base-line hemodynamic data had been obtained. At the end of the pacing period, a transmural biopsy was taken, frozen in liquid nitrogen, and sectioned into subepicardial, midmyocardial, and subendocardial layers. ATP, phosphocreatine, lactate, and glycogen were extracted and analyzed. Significant (P less than 0.001) transmural gradients of each of these metabolites existed in the control group. Pacing had no significant (P greater than 0.2) effect on any metabolite from layer to layer at 200 or 250 beats/min. However, indices of heart work (i.e., contractility (dP/dt), stroke work, and stroke volume) demonstrated significant reductions (P less than 0.01) due to pacing, while circumflex artery blood flow increased more than twofold (P less than 0.001) at the highest rate. These data suggest that physiologic autoregulation occurred during pacing and protected the subendocardium from stress-induced ischemic insult.

Topics: Adenosine Triphosphate; Animals; Cardiac Output; Coronary Disease; Dogs; Female; Glycogen; Heart Rate; Heart Ventricles; Lactates; Male; Myocardium; Phosphocreatine; Tachycardia

Ischemia in the isolated perfused rat heart resulted in an increase in coronary vascular resistance. Studies were undertaken to determine the effect of hyaluronidase and methylprednisolone on this increase in resistance as well as on glycolytic rate and mechanical function of ischemic hearts. Neither hyaluronidase nor methylprednisolone affected the rate of glucose utilization in working perfused control or ischemic rat hearts. However, both agents prevented a reduction in coronary flow during a 2-hour ischemic period. Associated with the higher coronary flows were higher tissue concentrations of creatine phosphate and lower concentrations of lactate. These agents also prevented accumulation of tissue water in the ischemic hearts. Such changes would appear to be beneficial to the ischemic heart, although mechanical function of post-ischemic hearts was not enhanced by the presence of either hyaluronidase or methylprednisolone. The results, however, suggest that the reduction in myocardial infarct size noted with hyaluronidase and methylprednisolone may be due to their prevention of further reduction of coronary flow in marginally eschemic tissue.

Topics: Adenosine Triphosphate; Animals; Body Water; Coronary Circulation; Coronary Disease; Glucose; Heart; Hyaluronoglucosaminidase; In Vitro Techniques; Lactates; Male; Methylprednisolone; Myocardial Contraction; Myocardium; Phosphocreatine; Rats; Vascular Resistance

A marked reduction in oxygen tension and adenosine triphosphate (ATP) content accompanies the early "pump" failure of the ischemic heart. However, it appears to be unlikely that decreased ATP supplies for energy-consuming reactions in the myocardial cell cause the observed decrease in myocardial contractility because of the high ATP-affinity of the substrate-binding sites of known energy-consuming reactions in the heart. Furthermore, lack of chemical energy for the contractile proteins and known ion pumps would tend to promote rigor and not a decrease in contractility. Recent evidence suggests that ATP at concentrations greater than those needed to saturate the substrate-binding sites of energy-consuming reactions can exert modulatory effects on ion fluxes. These modulatory effects of ATP could allow a less severe decrease in ATP concentration to inhibit both calcium entry into the myocardial cell and calcium efflux from the sarcoplasmic reticulum. In addition, the large amounts of phosphate liberated from phosphocreatine and ATP could, by causing formation of insoluble calcium-phosphate precipitates, trap calcium in the sarcoplasmic reticulum and mitochondria in the ischemic myocardium. These proposed explanations for the early "pump" failure in the ischemic heart, together with other theories such as intracell acidosis, appear to warrant further study.

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Coronary Disease; Myocardial Contraction; Myocardium; Phosphates; Phosphocreatine

Topics: Adenosine; Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Blood Pressure; Coronary Disease; Disease Models, Animal; Hypoxanthines; Hypoxia; In Vitro Techniques; Inosine; Male; Microspheres; Myocardial Contraction; Myocardium; Perfusion; Phosphocreatine; Polysaccharides; Rats; Sepharose

Topics: Adenine Nucleotides; Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Blood Pressure; Coronary Disease; Dogs; Female; Glucosephosphates; Heart Rate; Lactates; Ligation; Male; Myocardium; Phosphocreatine; Pyruvates; Water

Topics: Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Coronary Vessels; Dogs; Electrocardiography; Female; Glycogen; Lactates; Ligation; Male; Microspheres; Myocardium; Phosphocreatine; Potassium; Sodium

Isolated working rat hearts were made ischemic by introducing a one-way aortic ball valve. After the ischemic period the hearts were perfused in a retrograde non-working way for 30 min. Flow rates, glycogen, ATP, and creatine-phosphate went down during the time of ischemia, whereas tissue lactate accumulated. For shorter periods of ischemia these values were normalized but after 30 min of ischemia the hearts seemed to be irreversibly damaged. There was a leakage of GOT, GPT, LDH, and CPK from all hearts when ischemic from 5 to 30 min. Different factors that might be of importance for the degree of ischemic injury were tested. The injury tended to be more severe at higher heart rates. Addition of adrenaline 10(-6)M resulted in excessive myocardial damage. A variation of pH from 7.1 to 7.7 did not alter the effects of the ischemic injury. One group of rats were injected with adrenaline for 8 weeks to simulate chronic stress. When hearts from these rats were made ischemic they were more prone to fail compared to controls. The failing hearts, on the other hand, had a lower leakage of enzymes, possibly due to a less severe myocardial damage. A high mechanical performance and a normal noradrenaline content of the hearts are key factors for the development of myocardial infarction, as indicated by this study.

Topics: Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Glycogen; Heart; Heart Rate; Hydrogen-Ion Concentration; Lactates; Male; Perfusion; Phosphocreatine; Rats

The isolated perfused working rat heart preparation has been used to study the effects of respiratory acidosis on myocardial metabolism and contractilly. Hearts were perfused with 5 mM glucose and 10(-2) U/ml of insulin in order to enhance metabolsim of glucose relative to that of fatty acids. After perfusion with Krebs bicarbonate medium at pH 6.6, hearts rapidly ceased performing external work and peak left ventricular pressure fell by 75% after 5 minutes. Oxygen consumption, rate of ATP generation and overall glycolytic flux also declined rapidly. After about 2 minutes of perfusion, the fall of glycolytic flux showed a partial reversal, which was largely accounted for by increased lactate production, so that glucose oxidation decreased further. The reversal of glycoltic flux could be accounted for by partial release of H+ inhibition of phospho-fructokinase by increased tissue levels of adenosine 5'-diphosphate (ADP), adenosine monophosphate (AMP) and P1 and decreased levels of adenosine triphosphate (ATP) and creatine phosphate. The increased proportion of glucose uptake converted to lactate together with an increase of the tissue lactate/pyruvate ratio could be accounted for by inhibition of the malate-aspartate cycle combined with tissue hypoxia. Lactate accumulated in the tissue as a result of a decreased permeability of the plasma membrane to lactate. Decreased oxygen delivery to the myocardium was caused by secondary constriction of the coronary vessels. In further experiments, the coronary flow was regulated by an external pump which delivered fluid at a controlled rate into the aortic cannula above the coronary arteries, and the degree of tissue hypoxia was monitored by measuring changes of pyridine nucleotide reduction state by surface fluorescence techniques. The effects of acidosis uncomplicated by possible hypoxia were compared directly with those produced by ischemic hypoxia. The effects of acidosis under these conditions were similar to those described above, and to those produced by ischemia. From these and other data it is concluded that the effects of ischemia are caused by a lowering of the intracellular pH, which decreases the rate of energy production relative to the rate of energy demand. However, it is suggested that the primary cause of the decreased peak systolic pressure with either acidosis or ischemia is not a result of a defect of energy metabolism, but is due to alteration of the calcium cycle of the heart. Possible causes o

Topics: Acidosis, Respiratory; Adenine Nucleotides; Adenosine Monophosphate; Animals; Coronary Circulation; Coronary Disease; Cytosol; Fatty Acids; Fructosephosphates; Glucose; Glucosephosphates; Heart Ventricles; Hydrogen-Ion Concentration; In Vitro Techniques; Lactates; Male; Myocardium; NAD; NADP; Oxygen Consumption; Phosphocreatine; Pressure; Pyruvates; Rats

The intact heart of a young rat was excised rapidly and cooled to 0 degree C; its energy-rich compounds were examined by 31P Fourier Transform nuclear magnetic resonance. The heart showed the characteristic spectrum of sugar phosphates, inorganic phosphate, phosphocreatine, and magniesium phates, inorganic phosphate, phosphocreatine, and magnesium ATP, characteristics of the energizing state of the nonbeating tissue. Warming to 30 degrees C imposes an energy load upon the heart consistent with short-term resumption of beating, concomitant intracellular acidosis, and decomposition of all detectable energy-rich compounds. The intracellular acidity causes a shift from pH 7.0 to 6.0. The effects of possible interferences with this pH measurement are considered. The method appears to have wide usefulness in cardiac infarct models for detecting the fraction of the total volume occupied by the infarct and for studying the effect of various proposed therapies upon this infarcted volume.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Myocardium; Phosphates; Phosphocreatine; Phosphorus; Rats

Insertion of a flow pump into the Langendorff retrograde perfusion apparatus has permitted the production of stable, graded ischemia in hearts whose hemodynamic and metabolic response may be evaluated. Ventricular pressures were monitored with a modified balloon and catheter-tip manometer system, and oxygen consumption , lactate and glucose metabolism, and tissue high-energy phosphate stores measured. A 15-min stabilization period in 56 paced hearts was followed by 15 min of either full, 40, 30, 20, or 10% coronary flow, after which the ventricular tissue was freeze-clamped for tissue assay. Tissue creatine phosphate fell progressively from 23.7 in full flow hearts to 9.9 mumol/g dry wt after 90% reduction in flow. This was accompanied by a graded reduction in ATP from 20.3 to 14.0 mumol/g dry wt and a rise in AMP from 1.1 to 2.6 mumol/g dry wt. Tissue lactate rose progressively from 22.3 to 60.1 mumol/g dry wt. Hemodynamic function correlated with coronary flow. This preparation offers an opportunity to study pharmacological and metabolic interventions in ischemic heart disease.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Disease Models, Animal; Glucose; Glycogen; Hemodynamics; In Vitro Techniques; Lactates; Male; Myocardial Contraction; Myocardium; Oxygen Consumption; Phosphocreatine; Rats

An isolated perfused working rat heart model was used to investigate the extent to which various protective agents, used either singly or in combination, were able to increase the resistance of the heart to periods of transient ischemia. The aim of the studies was to develop a solution which, if infused into the coronary vessels just prior to the onset of ischemia, would rapidly induce arrest and would also counteract several of the deleterious cellular changes known to occur during myocardial ischemia. Agents with induce cardiac arrest, modify cellular ion loss, affect substrate utilization, energy production and energy stores, affect coronary vessel diameter and cell swelling, prevent dysrhythmias, and affect metabolic rate were investigated. The additive effects of these agents were evaluated. An aqueous solution was formulated which contained high concentrations of potassium and magnesium, in combination with adenosine triphosphate, creatine phosphate and procaine. This solution increased the recovery of the ischemic (37 degrees C for 30 min) rat heart from 0% to 93%. The safe period of ischemia could be further increased by the use of hypothermia.

Topics: Action Potentials; Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Drug Therapy, Combination; Energy Metabolism; Glucose; Heart Arrest, Induced; Hemodynamics; Hypothermia, Induced; Insulin; Male; Myocardium; Perfusion; Phosphocreatine; Rats; Water-Electrolyte Balance

Studies of ischaemic myocardium following occlusion of coronary arterial branches revealed a substantial decline in creatine phosphate, adenosine triphosphate, and total adenine nucleotide contents over 40 min. Contents of nucleotide breakdown derivatives increased significantly but transiently. Contractile force declined rapidly and stabilized at a low level. In nonischaemic muscle following occlusion creatine phosphate, adenosine triphosphate, and total nucleotide contents declined rapidly, although not to the degree seen in ischaemic muscle. Contents of derivatives increased only slightly. Contractile force increased.

Topics: Adenine Nucleotides; Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Coronary Disease; Dogs; Female; Male; Myocardial Contraction; Myocardium; Phosphocreatine

Physical training has been advocated to minimize the problems associated with coronary heart disease; however, the responsible mechanisms are obscure. Rats trained to run on a treadmill were subjected to acute conditions of hypoxia and myocardial ischaemia. Trained rats were better able to maintain a higher level of cardiac performance (dP/dt max) after hypoxia than non-trained rats, but no advantages were apparent after ischaemia. Biochemical data showed no myocardial differences between the groups in oxygen utilization or energy availability.

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Coronary Disease; Heart; Heart Rate; Hypoxia; Lactates; Male; Mitochondria, Muscle; Myocardium; Phosphocreatine; Physical Conditioning, Animal; Rats

An analysis of the main concepts of the pathogenesis of heart muscle insufficiency under ischaemia was conducted. None of the hypotheses postulating the invariability of the energy supply to the myofibrills was shown to explain the fast reduction of the contractility of the ischaemic myocardium. These hypotheses are based on the experimental fact of the ATP level in the myocardium practically undergoing no reduction under ischaemia. At the same time, one of the earliest changes in the heart muscle under ichaemia consists in creatine phosphate concentration reduction that correlates with the decrease in the contractility. The recently obtained data indicate that the energy synthesized in the mitochondria of the cardiac muscle is carried away from them in the form of energy of creatine phosphate molecules that is later used for ATP synthesis in the myofibrill creatine phosphokinase reaction. A scheme is suggested that implies that under ischaemia severe changes in the energy supply consisting in creatine phosphate synthesis reduction are the leading factor in the pathogenesis resulting on the early stages of the process in a reduction of the contractility, and on the later ones--in irreversible damages of the membrane systems and cell destruction.

Topics: Adenosine Triphosphate; Calcium; Coronary Disease; Energy Metabolism; Heart; Humans; Hypoxia; Mitochondria, Muscle; Models, Biological; Myocardial Contraction; Myocardium; Myofibrils; Phosphocreatine

Topics: Adenine Nucleotides; Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Amino Acids; Animals; Coronary Disease; Guanosine Triphosphate; Hypoxia; Muscle Proteins; Myocardium; Perfusion; Phosphocreatine; Rats

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Coronary Disease; Guanosine Triphosphate; Hypoxia; Insulin; Myocardium; Phosphocreatine; Proteins

The effects of metabolic accumulation on myocardial metabolism during global heart oxygen deprivation were evaluated in a working in situ swine heart preparation with controlled total coronary blood flow. Myocardial oxygen consumption was depressed to a similar extent by either reducing total coronary flow 60 per cent (ischemia, low coronary perfusion) in 10 swine or by decreasing coronary perfusate PO2 to 30 mm. Hg at normal flows (hypoxemia, high coronary perfusion) in 13 swine. Compared with findings in 13 control hearts, ischemia significantly (p less than 0.05) decreased myocardial oxygen consumption (640 to 390 mumole per hour per gram), glucose uptake (185 to 16 mumole per hour per gram), and free fatty acid consumption (32 to 17 mumole per hour per gram). ttissue levels of glycogen, creatine phosphate, and adenosine triphosphate (tatp) were significantly reduced (p less than 0.005), and tissue lactate, adenosine diphosphate (ADP), and adenosine monophosphate (AMP) were increased (p less than 0.001). During hypoxemia, glucose uptake was increased (240 mumole per hour per gram) and free fatty acid consumption was somewhat less depressed (19 mumole per hour per gram). Creatine phosphate and ATP were higher than with ischemia (p less than 0.01), and lactate, ADP, and AMP accumulations were less (p less than 0.01). Thus, in the period immediately following myocardial oxygen deprivation, inadequate coronary perfusion caused greater metabolic buildup which inhibited myocardial substrate utilization and energy production. High coronary perfusion, even though the perfusate was unoxygenated, was associated with greater preservation of substrate utilization, higher levels of high-energy phosphates, less accumulation of metabolic products, and a longer survival. These data suggest a critical role of coronary perfusion in protecting myocardial metabolism in the immediate period following global heart hypoxia.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Coronary Disease; Disease Models, Animal; Female; Glucose; Glycogen; Heart; Hemodynamics; Hypoxia; Lactates; Male; Myocardial Revascularization; Myocardium; Oxygen Consumption; Phosphocreatine; Swine

The effect of ischemia on synthesis of myocardial proteins was investigated using a model of perfusion in which low levels of coronary flow were provided to paced hearts worked against a closed aortic outflow tract. These conditions rapidly produced ischemia and ventricular failure, as evidence by reduced coronary flow, increased left atrial pressure, and decreased pressure development. Protein synthesis was inhibited in a subsequent 1-hour period, during which a minimal coronary flow was maintained by retrograde perfusion. ATP, GTP, and creatinine phosphate were depleted in ischemic hearts and AMP accumulated. Production and accumulation of lactate within the tissue increased, whereas palmitate uptake was inhibited. The inhibition of protein synthesis was not associated with reduced levels of intracellular amino acids. During ischemia, decreased levels of ribosomal subunits as compared to paced or unpaced aerobic hearts suggested that peptide chain elongation was slow relative to initiation. Provision of insulin further reduced subunit levels but did not increase protein synthesis, suggesting that the hormone did not prevent inhibition of peptide chain elongation in energy-poor hearts.

Topics: Aerobiosis; Anaerobiosis; Animals; Coronary Circulation; Coronary Disease; Disease Models, Animal; Hypoxia; Lactates; Male; Muscle Proteins; Myocardium; Perfusion; Phenylalanine; Phosphocreatine; Purine Nucleotides; Rats

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Depression, Chemical; Disease Models, Animal; Dogs; Glucosephosphates; Glycogen; Glycolysis; Heart; Lactates; Myocardium; Nitroglycerin; Phosphocreatine; Phosphorylases

After establishing a model of ischemia, perfusion in the ischemic area was considerably disturbed. Examination by means of 133xenon-clearance after intramyocardiac injection showed strongly delayed flowing-off compared with controls. Counterpulsation accelerates the flowing-off (perfusion). Untreated control animals reveal after inducing the model ischemia a crucial decrease of ATP concentration and an excessive increase of lactate concentration in the ischemic area. Counterpulsation may inhibit further decrease of ATP in the ischemic area.

Topics: Adenosine Triphosphate; Animals; Assisted Circulation; Coronary Disease; Disease Models, Animal; Humans; Intra-Aortic Balloon Pumping; L-Lactate Dehydrogenase; Lactates; Ligation; Metabolic Clearance Rate; Myocardium; Perfusion; Phosphocreatine; Time Factors; Xenon Radioisotopes

In the nonischemic canine left ventricle, levels of glycogen, glucose-6-phosphate (G6P), and lactate, and phosphorylase activity in the endocardial layers were higher than those in the epicardial layers, but the phosphocreatine (PCr) level in the endocardial layers was lower than that in the epicardial layers, and there were no differences in the adenosine triphosphate (ATP) level between the endo- and epicardial layers. Upon ligation of a small branch of the left descending coronary artery, levels of glycogen and PCr decreased, while those of G6P and lactate increased, and the activity of phosphorylase increased. The level of ATP was not affected by the coronary ligation. Thus the coronary ligation accelerated the glycogenolysis and glycolysis in the myocardium without affecting ATP level, and the acceleration in metabolism in the endocardial layers was more rapid and marked than that in the epicardial layers.

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Coronary Artery Bypass; Coronary Disease; Dogs; Endocardium; Female; Glucosephosphates; Glycogen; Heart Rate; Ligation; Male; Pericardium; Phosphocreatine; Phosphorylases

Intracoronary injection of 14 mcg. of tetrodotoxin into the ischemic isolated rat heart resulted in immediate cessation of mechanical activity. Upon reperfusion with oxygenated, modified Krebs-Henseleit bicarbonate buffer in a modified Langendorff apparatus, all hearts recovered normal rate, rtythm, and contractile vigor after up to 60 minutes of ischemia. In contrast, all hearts not administered tetrodotoxin showed bradycardia, irregular rhythm, and weak contraction upon reperfusion after 30 and 45 minutes of ischemia; after 60 minutes, no mechanical activity was evident. The improved cardiac function following ischemia in the tetrodotoxin-treated hearts was associated with persistence of normal adenosine triphosphate (ATP) levels after up to 30 minutes of ischemia and normal or elevated creatine phosphate (CP) levels after up to 60 minutes of ischemia. On the other hand, ATP and CP levels progressively declined to reach 50 per cent of normal values after 30 minutes in the ischemic hearts without tetrodotoxin. These findings indicate that postarrest ATP and CP levels play an important role in myocardial recovery after ischemic arrest.

Topics: Adenosine Triphosphate; Animals; Bicarbonates; Buffers; Coronary Disease; Disease Models, Animal; Heart; Heart Arrest; Heart Conduction System; Heart Rate; Myocardium; Perfusion; Phosphocreatine; Rats; Tetrodotoxin; Time Factors

The effects of coronary reperfusion on recovery of regional myocardial contractility and high energy pegmental changes in myocardial contractility were measured by means of a strain gauge-tipped, two-pronged catheter probe that measures myocardial fiber shortening. The curves of contraction are sensitive to the effects of ischemia. Coronary occlusion resulted in a rapid replacement of fiber shortening by passive fiber lengthening. If coronary occlusion was released and blood flow restored within 45 minutes, myocardial contractility returned promptly; adenosine triphosphate and creatine phosphate values were restored to normal. With coronary occlusion of 1 hour or longer, contractility failed to return in the immediate postperfusion period, but delayed return was recorded after 2 weeks of reperfusion. The extent of such recovery varied with the duration of preceding occlusion. Thus, reperfusion after 1 hour of occlusion was followed by return of fiber shortening over the entire reperfused region. With 2 hours of occlusion, recovery occurred over 75 percent of the reperfused myocardium. With 3 hours of occlusion followed by reperfusion, recovery of contractility was only partial, comprising approximately 60 percent of the reperfused region. High energy phosphate content of the reperfused myocardium showed a similar pattern of recovery. With occlusion of longer duration, reperfusion failed to restore contractility to any significant extent. These findings indicate that reperfusion after coronary occlusion of 1 to 3 hours may restore contractility over a period of 2 weeks, but the extent of such recovery diminishes with the increase in the duration of occlusion.

Topics: Adenosine Triphosphate; Animals; Cardiac Catheterization; Coronary Circulation; Coronary Disease; Dogs; Heart; Myocardial Contraction; Myocardial Infarction; Myocardial Revascularization; Myocardium; Phosphocreatine

The capacity for recovery of the normothermic left ventricular myocardium from a regional complete ischemia (RCI) was investigated using changes in the myocardial metabolic status (ATP, ADP, AMP, creatine phosphate (CrP), free creatine, glycogen, glucose, lactate) and alterations of the morphology as parameters. In dogs, an area of the anterior wall of the left ventricular myocardium was temporarily deprived completely of its blood supply by 5--7 overlapping ligatures extending into the heart cavity. The metabolites of the adenylic acid-CrP system returned to normal tissue levels after 30 and 60 min of RCI within 14 and 35 days of recovery, respectively; restoration averaged 82% after 100 min, 74% after 140 min, and 38% after 180 min of RCI after 5 weeks of recovery. At the same time glycogen amounted to 163% after 100 min, 114% min, and 65% after 180 min of RCI. The biochemical data correlated well with the structural changes in the affected myocardium, especially with the amount of de- and regenerating heart muscle cells. These obviously were functionally defect and were not comparable with normal structured and functioning heart muscle cells.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Cell Nucleus; Collagen; Coronary Disease; Creatine; Dogs; Female; Glucose; Glycogen; Heart; Heart Ventricles; Lactates; Ligation; Male; Mitochondria, Muscle; Myocardium; Myofibrils; Phosphocreatine; Time Factors; Ventricular Function

To determine whether transmural metabolite gradients develop in the contracting, ischemic left ventricle due to factors other than a nonuniform distribution of myocardial blood flow, right and left coronary artery inflow was completely stopped with vessel occluders in open-chest dogs for 15 or 30 seconds before a transmural myocardial tissue sample was obtained for regional analysis of creatine phosphate, adenosine triphosphate (ATP), and lactate. Heart rate was controlled, and the decline in left ventricular systolic pressure during the period in which coronary blood flow was stopped was attenuated by aortic constriction. Studies were also performed in dogs that were (1) pretreated with propranolol, (2) subjected to ventricular fibrillation, and (3) volume loaded. Control studies revealed no transmural metabolite gradients in the normally perfused ventricle, but creatine phosphate was slightly lower in the inner region than it was in the outer and middle ventricular wall regions. With coronary blood flow stopped for 30 seconds, a significant lactate gradient, increasing from the outer to the inner region, was present. Propranolol-treated dogs with their coronary blood flow stopped for 30 seconds also exhibited a lactate gradient, but dogs with ventricular fibrillation and their coronary blood flow stopped for 30 seconds did not. Volume-loaded dogs with their coronary blood flow stopped for only 15 seconds had a significant lactate gradient. Reciprocal gradients occurred in creatine phosphate but not in ATP. The findings suggest that the contracting ventricle uses energy unevenly and that in myocardial ischemia one of the factors causing greater subendocardial vulnerability is a greater energy need in this region.

Topics: Adenosine Triphosphate; Animals; Cardiac Volume; Coronary Circulation; Coronary Disease; Dogs; Endocardium; Energy Metabolism; Heart; Heart Ventricles; Lactates; Male; Myocardial Contraction; Myocardium; Phosphocreatine; Propranolol; Ventricular Fibrillation

Acute myocardical ischemia was produced by ligating the midlevel left anterior descending coronary artery for 17 min in anesthetized dogs. Epicardial electrocardiograms were recorded from 15 sites surrounding the area of left anterior descending coronary artery ligation with a smooth tip, rounded epicardial electrode. Sites of ST segment elevation and isoelectric sites within the grossly ischemic portion of the left ventricle were needle biopsied to obtain tissue samples of less than 6 mg wet weight to assess myocardial metabolism at these precise sites. Epicardial areas of ST segment elevation had marked lactate accumulation and high energy phosphate depletion. Isoelectric sites were areas of either no lactate accumulation or mild lactate accumulation and high energy phosphate concentrations that were greater than those found at site of ST segment elevation. Thus, the data obtained indicate that epicardial sites of ST segment elevation are locations of profound anaerobic metabolism and of both epicardial and endocardial ischemia.

Topics: Acute Disease; Adenosine Triphosphate; Coronary Circulation; Coronary Disease; Electrocardiography; Hypoxia; Lactates; Membrane Potentials; Myocardium; Phosphocreatine

In the left ventricle of the dog, a transmural difference is present in the normal state for various metabolites and persists in the experimental conditions studied. ATP stores are maintained both in the endo-as well as epicardium at the expense of PC. This is true for systemic hypoxia, hemorrhagic shock, and isoproterenol infusion. In severe ischemia, however, endocardial ATP is lower, while the transmural gradient for PC is increased due to a marked decrease in endocardial PC content. Our studies underline the importance of nonhomogeneity of the left ventricular wall and demonstrate that the subendocardium is more subject to anaerobic metabolism, especially when coronary perfusion pressure is decreased.

Topics: Adenine Nucleotides; Animals; Cardiomyopathies; Coronary Disease; Dogs; Hypoxia; Isoproterenol; Lactates; Mitochondria, Muscle; Myocardium; Phosphocreatine; Shock, Hemorrhagic

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Coronary Vessels; Dipyridamole; Dogs; Glucosephosphates; Glycogen; Lactates; Ligation; Myocardium; Phosphocreatine; Phosphorylases

Isolated perfused working rat hearts were subjected to elective cardiac arrest for 20 or 30 min. Various methods of arrest were studied, either singly or in combination and with or without coronary perfusion. The functional recovery of the heart following the termination of arrest was found to be related to the concentration of ATP and creatine phosphate in the myocardium at the end of the period of arrest. In turn, these concentrations were dependent upon the method used to induce arrest. Normothermic ischemic arrest led to a marked reduction in high energy phosphates and a poor functional recovery. In contrast, coronary perfusion with hypothermic solutions or solutions containing high concentrations of potassium, induced arrest without depleting ATP or creatine phosphate. These procedures conferred considerable protection on the myocardium and thus permitted good recoveries. The energy status and recovery associated with ischemic arrest could be improved by combining the ischemia with hypothermia or potassium arrest. The latter, while increasing recovery significantly, still failed to afford complete protection to the myocardium. Potassium chloride gave greater protection than potassium citrate. When topical hypothermia was combined with ischemia, a time and temperature relationship was demonstrated but effective protection could only be obtained with severe topical hypothermia over a relatively short time period. The results stress the importance of maintaining high energy phosphates during arrest, and this requires the provision of a continuous supply of oxygen and nutrient, which may perhaps be best achieved by ensuring continuous and adequate coronary perfusion.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Heart Arrest, Induced; Hypothermia, Induced; Male; Models, Biological; Myocardial Contraction; Perfusion; Phosphocreatine; Potassium; Rats

Isolated working rat hearts were made ischemic for 5, 10, and 30 minutes respectively. After the ischemic period, all hearts were perfused in a retrograde nonworking way for 30 minutes. During the 5 first minutes of ischemia, there was a marked fall of cardiac output and coronary flow. A significant release of GOT was seen and this was more marked after longer periods of ischemia. Addition of adrenaline to the perfusate increased the enzyme release. Pacing at 400/minute, high preload, high afterload, acidosis, or alkalosis did not alter enzyme release. Glycogen, ATP and CrP levels were depressed at the end of the ischemic period, but were seen to be rising again during the retrograde perfusion. This study indicates that myocardial tissue may release enzymes without being irreversibly damaged.

Topics: Adenosine Triphosphate; Animals; Aspartate Aminotransferases; Coronary Circulation; Coronary Disease; Creatine Kinase; Glycogen; Hemodynamics; L-Lactate Dehydrogenase; Lactates; Male; Phosphocreatine; Rats

Inhibition of adenine nucleotide translocase by elevated levels of long chain acyl-CoA esters has been shown to occur during the onset of ischemia in experiments conducted on dogs. Other findings indicate that, as a consequence of translocase inhibition, the production of mitochondrial creatine phosphate was abolished and, in this manner, respiration was slowed to state 4 or an ischemic-like condition. A variety of biochemical, hemodynamic, and ultrastructural evidence further suggest that this inhibition of adenine nucleotide transport in and out of the heart mitochondria may be the initial and key disturbance which "triggers" the more drastic metabolic changes known to occur as the degree of ischemia becomes more severe. The mitochondrial "damage" caused by long chain acyl-CoA ester inhibition of adenine nucleotide translocase appears to be reversible by carnitine.

Topics: Adenosine Diphosphate; Animals; Atractyloside; Carnitine; Cattle; Coenzyme A; Coronary Disease; Dogs; Hemodynamics; Mitochondria, Muscle; Mitochondrial ADP, ATP Translocases; Nucleotidyltransferases; Oleic Acids; Oxygen Consumption; Phosphocreatine; Time Factors

Regional contractility measured as myocardial fiber shortening ceased 15-30 sec after coronary occlusion; myocardial ATP content was unaltered at this time. Contractility returned promptly if occlusion was released within 45 min. With occlusion of 1-3 hr, delayed recovery of contractility was observed 2 weeks after reperfusion; the extent of recovery diminshed with increasing period of occlusion. Concomitantly, there was parallel recovery of synthesis of ATP and creatine phosphate (CP) in reperfused myocardium.

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Dogs; Heart; Myocardial Contraction; Myocardium; Perfusion; Phosphocreatine

After local complete ischemia at normothermia of 60, 100, 140, and 180 min duration the status of the adenylic acid-creatine phosphate system in the canine myocardium recovered to 98, 85, 74, and 30 percent of the control values, whereas glycogen was restored even more. In the infarcted myocardium the extent of alterations of the metabolic status was a function of the residual blood flow. Deviations from a regular metabolic status developed if the blood flow dropped below about 35 ml/min/100 gm. This critical flow rate is expected to vary with the energy requirement of the heart, but it is in keeping with results obtained by Rudolph and coworkers (personal communication) who found that patients with a myocardial blood flow below 30 ml/min/100 gm had a life expectancy of less than 1 month. In the nonaffected myocardium, both in experiments with local complete ischemia and in experiments with infarction, the metabolic status was always within normal ranges. This is in contrast to results published by Gudbjarnason (1971/1972) and Gudbjarnason, Puri, and Mathes (1971), who found that in noninfarcted myocardium tissue levels of ATP and creatine phosphate decreased to about 50 percent of the control values and that there was no restoration to normal values within 10 days after infarction.

Topics: Adenosine Monophosphate; Animals; Coronary Disease; Creatine; Disease Models, Animal; Dogs; Glycogen; Heart Ventricles; Lactates; Myocardial Infarction; Myocardium; Phosphocreatine; Time Factors

Topics: Adenine Nucleotides; Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Coronary Circulation; Coronary Disease; Disease Models, Animal; Heart; Heart Failure; Lactates; Male; Myocardium; Oxygen Consumption; Phosphocreatine; Rats; Regional Blood Flow; Time Factors

Topics: Adenosine Triphosphate; Animals; Arteriosclerosis; Cholesterol; Coronary Disease; Heart; Lactates; Microscopy, Electron; Mitochondria, Muscle; Mitochondrial Swelling; Myocardium; Oxygen Consumption; Phosphocreatine; Radiation Effects; Swine

Topics: Acute Disease; Adenine Nucleotides; Aerobiosis; Anaerobiosis; Animals; Coronary Disease; Coronary Vessels; Disease Models, Animal; Dogs; Fatty Acids; Glucose; Glycolysis; Hydrogen-Ion Concentration; Lactates; Mitochondria, Muscle; Models, Biological; Myocardial Infarction; Myocardium; Phosphocreatine

Topics: Acute Disease; Adenosine Triphosphate; Animals; Coronary Disease; Coronary Vessels; Disease Models, Animal; Dogs; Lactates; Myocardial Infarction; Myocardium; Phosphocreatine; Time Factors

Topics: Adult; Aged; Coronary Disease; Digitalis Glycosides; Female; Heart Failure; Humans; Male; Middle Aged; Phosphocreatine

Topics: Aged; Alcohols; Cardiac Complexes, Premature; Chronic Disease; Coronary Disease; Electrocardiography; Female; Heart Diseases; Humans; Male; Middle Aged; Myocardial Infarction; Phosphocreatine; Tachycardia

Topics: Aged; Cardiac Complexes, Premature; Chronic Disease; Coronary Disease; Electrocardiography; Female; Heart Diseases; Heart Failure; Humans; Male; Middle Aged; Myocardial Infarction; Phosphocreatine; Tachycardia

Topics: Actins; Adenosine Triphosphatases; Adenosine Triphosphate; Anaerobiosis; Calcium; Coronary Disease; Glycolysis; In Vitro Techniques; Muscle Proteins; Myocardium; Myosins; Phosphocreatine; Potassium; Sodium; Tropomyosin

Topics: Anaerobiosis; Animals; Blood Pressure; Coronary Disease; Heart; Heart Conduction System; In Vitro Techniques; Ligation; Male; Muscle Contraction; Myocardial Infarction; Perfusion; Phosphocreatine; Rabbits; Rats; Stimulation, Chemical

Topics: Adenine Nucleotides; Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Blood Sedimentation; Chinchilla; Coronary Disease; Creatine; Glycogen; Heart; Ketoglutaric Acids; Malates; Mast Cells; Microcirculation; Mitochondria, Muscle; Myocardium; Oxidative Phosphorylation; Oxygen Consumption; Phosphocreatine; Pyruvates; Rabbits; Succinates; Transferases

Topics: Adenosine Triphosphate; Aerobiosis; Animals; Coronary Disease; Coronary Vessels; Dogs; Glycolysis; Kinetics; Myocardium; Oxygen Consumption; Perfusion; Phosphocreatine

Topics: Adenosine Triphosphate; Anaerobiosis; Animals; Coronary Disease; Dogs; Energy Transfer; Glycolysis; Heart Rate; Kinetics; Lactates; Myocardial Infarction; Myocardium; Phosphocreatine

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Mitochondria, Muscle; Myocardium; Phosphocreatine

Topics: Adenine Nucleotides; Animals; Coronary Disease; Dogs; Female; Heart Ventricles; Hyperemia; Myocardium; Phosphocreatine; Rats; Rats, Inbred Strains; Vasodilation

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Dogs; Myocardium; Phosphates; Phosphocreatine

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Animals; Biopsy; Coronary Disease; Coronary Vessels; Creatine Kinase; Dogs; Energy Transfer; Heart; Ischemia; Kinetics; Lactates; Ligation; Mitochondria, Muscle; Myocardial Infarction; Myocardium; Phosphocreatine; Pyruvates

Topics: Adenosine Triphosphatases; Adenosine Triphosphate; Calcium; Coronary Disease; Heart Failure; Humans; Muscle Contraction; Muscle Proteins; Myocardium; Phosphocreatine; Water-Electrolyte Balance

Topics: Adenine Nucleotides; Adenosine Triphosphate; Animals; Coronary Disease; Creatine; Depression, Chemical; Fructose-Bisphosphate Aldolase; Glucokinase; Glucose-6-Phosphate Isomerase; Glucosephosphate Dehydrogenase; Glutathione Reductase; Guinea Pigs; Hexokinase; In Vitro Techniques; L-Lactate Dehydrogenase; Myocardium; Phosphocreatine; Phosphogluconate Dehydrogenase; Phosphoglycerate Kinase; Propiophenones; Pyruvate Kinase

Topics: Adenosine Triphosphate; Animals; Coronary Disease; Dogs; Heart Arrest; Heart Arrest, Induced; Hypothermia, Induced; Microscopy, Electron; Myocardium; Perfusion; Phosphocreatine; Time Factors

Topics: Arrhythmias, Cardiac; Coronary Disease; Heart Failure; Humans; Phosphocreatine

Topics: Adenine Nucleotides; Adenosine Triphosphate; Animals; Coronary Disease; Creatine; Enzymes; Guinea Pigs; Hydro-Lyases; In Vitro Techniques; Isomerases; Myocardium; Norepinephrine; Oxidoreductases; Phosphates; Phosphocreatine; Phosphotransferases; Transaminases

Topics: Adenine Nucleotides; Adenosine Triphosphate; Animals; Blood Flow Velocity; Coronary Disease; Coronary Vessels; Guinea Pigs; Heart; Humans; Ischemia; Isotonic Solutions; Myocardium; Nitrogen; Oxygen; Oxygen Consumption; Perfusion; Phosphocreatine

Topics: Animals; Coronary Disease; Dogs; Heart Failure; Hemodynamics; Phosphocreatine

Topics: Adenosine Triphosphatases; Adenosine Triphosphate; Animals; Blood Glucose; Carbohydrate Metabolism; Coronary Disease; Dogs; Glycogen; Histocytochemistry; Lactates; Myocardium; Oxygen Consumption; Phosphocreatine; Phosphorus; Polarography; Pyruvates