angiotensin-i and Cardiac-Output--Low

Angiotensin-(1-7) is a product of angiotensin processing that has been proposed to have vasodepressor effects, both on its own and in combination with bradykinin, which may be pathophysiologically and therapeutically important. Despite this, there has been very little examination of its effects in humans and none in heart failure patients or in other patients treated with ACE inhibitors. We therefore sought to determine the effects of angiotensin-(1-7) in patients with heart failure treated with an ACE inhibitor, as well as any interaction with the effects of bradykinin. A locally active dose of angiotensin-(1-7), alone and in combination with bradykinin, was infused into the nondominant brachial artery while forearm blood flow was measured by venous occlusion plethysmography in 8 patients with heart failure treated with ACE inhibitors. Although bradykinin on its own caused profound vasodilation, there was no effect of angiotensin-(1 to 7) on its own or any effect of angiotensin-(1-7) on the response to bradykinin. We conclude that angiotensin-(1-7) is biologically inactive in the forearm circulation of patients with heart failure treated with an ACE inhibitor. The contrast between these findings and previously reported preclinical findings calls into question the relevance of angiotensin-(1-7) to the hemodynamic effects of ACE inhibitors.

Topics: Aged; Angiotensin I; Angiotensin II; Angiotensin-Converting Enzyme Inhibitors; Blood Pressure; Bradykinin; Cardiac Output, Low; Dose-Response Relationship, Drug; Drug Interactions; Female; Heart Rate; Humans; Male; Peptide Fragments

Previous studies in heart failure (CHF) after temporary diuretic withdrawal have suggested that perindopril is associated with no first dose hypotension in comparison with other ACE inhibitors (ACEI) or placebo. The aim of this study was to explore further the profile of perindopril during chronic dosing.. We report the effects of acute and chronic (8 weeks) treatment with the ACE inhibitor perindopril (Per, 2-->4 mg daily) or placebo (P) in a double-blind parallel group study of 24 diuretic treated patients (17M; 67 +/- 8 years, 80 +/- 17 kg) with ischaemic cardiomyopathy (fractional shortening, 19 +/- 5%; radionuclide ejection fraction, 31 +/- 3%). Baseline biochemical, hormonal (ACE, Ang I, Ang II), isotopic renal function (GFR, ERPF, ECFV), pretreatment diuretic dose and heart failure scores were similar between groups. Concomitant cardiac treatments remained unchanged and diuretic withdrawal was not used to introduce treatment.. There were no significant effects on electrolytes, liver function tests, serum or erythrocyte magnesium. There was no significant first dose fall in SBP over 6 h) (P, baseline 137 +/- 18; min 115 +/- 16 mmHg; Per, baseline 137 +/- 15; min 118 +/- 17 mmHg). Neither supine nor erect BP was significantly affected by chronic treatment (P, erect baseline 134 +/- 23/76 +/- 10 to 124 +/- 41/74 +/- 10 mmHg; Per, baseline 135 +/- 21/76 +/- 14 to 128 +/- 22/70 +/- 12 mmHg, P=NS). Active treatment was associated with significant ACE inhibition (P, baseline 47 +/- 17 to 43 +/- 17; Per baseline 49 +/- 15 to 14 +/- 7); aldosterone (P, baseline 337 +/- 179 to 375 +/- 306; Per, baseline 335 +/- 357 to 293 +/- 155 pg ml(-1)) and Ang II suppression (P, baseline 9 +/- 9 to 20 +/- 39; Per baseline 10 +/- 9 to 3 +/- 3 pM). Isotopic renal function was unaffected by either treatment.. At this dose (2-4 mg orally) chronic perindopril therapy has no significant effect on blood pressure or renal function. Sustained neurohormonal suppression of ACE and AII occurred without evidence of AII reactivation. A lack of effect on BP at these doses may make perindopril suitable for study in unstable patients with acute HF or useful in those patients where there are concerns over ACEI induced hypotension.

Topics: Aged; Aldosterone; Angiotensin I; Angiotensin II; Angiotensin-Converting Enzyme Inhibitors; Blood Pressure; Cardiac Output, Low; Chronic Disease; Depression, Chemical; Female; Humans; Indoles; Kidney Function Tests; Male; Middle Aged; Perindopril

To investigate the role of angiotensin-converting enzyme-related carboxypeptidase (ACE2) in angiotensin peptide metabolism in the human coronary circulation.. Angiotensin I and angiotensin II, and their respective carboxypeptidase metabolites, angiotensin-(1-9) and angiotensin-(1-7), were measured in arterial and coronary sinus blood of heart failure subjects receiving angiotensin-converting enzyme (ACE) inhibitor therapy and in normal subjects not receiving ACE inhibitor therapy. In addition, angiotensin I, angiotensin II and angiotensin-(1-7) were measured in arterial and coronary sinus blood of subjects with coronary artery disease before, and at 2, 5 and 10 min after, intravenous administration of ACE inhibitor.. In comparison with normal subjects, heart failure subjects receiving ACE inhibitor therapy had a greater than 40-fold increase in angiotensin I levels, but angiotensin-(1-9) levels were low (1-2 fmol/ml), and similar to those of normal subjects. Moreover, angiotensin-(1-7) levels increased in parallel with angiotensin I levels and the angiotensin-(1-7)/angiotensin II ratio increased by 7.5-fold in coronary sinus blood. Intravenous administration of ACE inhibitor to subjects with coronary artery disease rapidly decreased angiotensin II levels by 54-58% and increased angiotensin I levels by 2.4- to 2.8-fold, but did not alter angiotensin-(1-7) levels or net angiotensin-(1-7) production across the myocardial vascular bed.. The failure of angiotensin-(1-9) levels to increase in response to increased angiotensin I levels indicated little role for ACE2 in angiotensin I metabolism. Additionally, the levels of angiotensin-(1-7) were more linked to those of angiotensin I than angiotensin II, consistent with its formation by endopeptidase-mediated metabolism of angiotensin I, rather than by ACE2-mediated metabolism of angiotensin II.

Topics: Adult; Angiotensin I; Angiotensin II; Angiotensin-Converting Enzyme 2; Angiotensin-Converting Enzyme Inhibitors; Angiotensins; Carboxypeptidases; Cardiac Output, Low; Case-Control Studies; Coronary Circulation; Drug Administration Schedule; Female; Humans; Male; Middle Aged; Peptide Fragments; Peptidyl-Dipeptidase A

The formation of angiotensin-(1-7) from either angiotensin (Ang) I or Ang II in failing human hearts is not well understood.. Angiotensinase activity in left and right ventricular membranes from 14 idiopathic dilated cardiomyopathy (IDC), 8 primary pulmonary hypertension (PPH), and 13 nonfailing human hearts was measured with either 125I-Ang I or 125I-Ang II as substrate. Ang-(1-7)-forming activity from 125I-Ang I was inhibited by thiorphan. With 125I-Ang II as substrate, Ang-(1-7) formation was inhibited by the ACE2-specific inhibitor C16. Western blotting with an anti-ACE2 antibody confirmed the presence of ACE2. Angiotensinase activity with 125I-Ang I as substrate was increased in failing IDC left ventricles (LVs) compared with nonfailing LVs (P<0.001). Ang-(1-7)-forming activity with 125I-Ang II as substrate was increased in both failing LVs and right ventricles (RVs) of IDC hearts and only in failing RVs of PPH hearts (PPH LV, 51.12+/-5.25; PPH RV, 89.97+/-11.21; IDC LV, 139.7+/-21.96; and IDC RV, 192.7+/-5.43; NF LV, 32.89+/-5.38; NF RV 40.49+/-10.66 fmol/min per milligram (P<0.05 PPH RV versus PPH LV; P<0.05 PPH RV versus NF RV; P<0.001 IDC LV versus NF LV; P<0.001 IDC RV versus NF RV).. Ang-(1-7)-forming activity from both Ang I and Ang II was increased in failing human heart ventricles but was mediated by at least two different angiotensinases. The first, which demonstrated substrate preference for Ang I, was neutral endopeptidase (NEP)-like. The second was ACE2, as demonstrated by Western blotting and inhibition of activity with C16.

Topics: Adult; Angiotensin I; Angiotensin II; Angiotensin-Converting Enzyme 2; Carboxypeptidases; Cardiac Output, Low; Female; Heart Ventricles; Humans; Male; Peptide Fragments; Peptidyl-Dipeptidase A; Up-Regulation

Chronic heart failure (CHF) induces peripheral vasoconstriction and impairs endothelium-dependent relaxation of large arteries. We investigated in a rat model of CHF (coronary artery ligation) 1) whether endothelial dysfunction also exists in resistance arteries, 2) whether this is associated with vascular morphological changes, and 3) the effect of angiotensin-converting enzyme (ACE) inhibition on these parameters. After 1 mo or 1 yr, CHF reduced the vasodilatory response to acetylcholine of isolated, perfused femoral and mesenteric artery segments. This impairment was more marked in femoral than in mesenteric arteries. However, CHF did not induce any arterial remodeling. Chronic treatment with the ACE inhibitor perindopril improved the response to acetylcholine and reduced media cross-sectional area and collagen density. Thus at the level of small peripheral arteries, CHF induces an endothelial dysfunction but does not affect vascular structure. ACE inhibition prevents the CHF-induced endothelial dysfunction and induces vascular remodeling. These changes could contribute to the observed beneficial effects of ACE inhibitors on hemodynamics and survival in CHF.

Topics: Acetylcholine; Angiotensin I; Angiotensin II; Angiotensin-Converting Enzyme Inhibitors; Animals; Cardiac Output, Low; Endothelium, Vascular; Femoral Artery; Hemodynamics; In Vitro Techniques; Indoles; Male; Myocardial Infarction; Nitroprusside; Perindopril; Rats; Rats, Wistar; Vasodilator Agents

Reduced preload and afterload to the heart are important effects of angiotensin converting enzyme (ACE) inhibitors in the treatment of congestive heart failure. However, since angiotensin II (Ang II) directly increases the strength of myocardial contraction, suppression of Ang II formation by ACE inhibitors could potentially reduce the beneficial effects of Ang II on the failing heart. To study how ACE inhibition suppresses cardiac Ang II formation in man, we characterized ACE-dependent and ACE-independent Ang II-forming pathways in eight normal and 24 failing human hearts obtained at cardiac transplantation. Ang II-forming activity in left ventricular (LV) membrane preparations was assessed by measuring the conversion of [125I]angiotensin I (Ang I) to [125I]Ang II. LV [125I]Ang II-forming activity in normal hearts (35.5 +/- 2.7 fmol/min/mg, n = 8) was not different from that in hearts from patients with ischemic cardiomyopathy (25.5 +/- 2.9 fmol/min/mg, n = 9) and was 48% lower (p less than 0.001) in hearts from patients with idiopathic cardiomyopathy (18.5 +/- 1.9 fmol/min/mg, n = 15).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adolescent; Adult; Angiotensin I; Angiotensin II; Captopril; Cardiac Output, Low; Female; Glycine max; Heart; Heart Ventricles; Humans; Male; Middle Aged; Myocardium; Peptidyl-Dipeptidase A; Reference Values; Trypsin Inhibitors

We examined the hypothesis that the positive inotropic effect of angiotensin I (Ang I) may be retained in the presence of angiotensin converting enzyme inhibitors so that it may have a direct beneficial effect on the heart. Accordingly, isolated perfused hearts (Langendorff preparation) of 300-day-old cardiomyopathic hamsters (a model of spontaneous cardiomyopathy) and age-matched normal hamsters (controls) were infused with Ang I in the presence of captopril; propranolol was added to the perfusing medium to block catecholamine-mediated effects of angiotensins on the heart. Left ventricular developed pressure and the rate of increase in left ventricular developed pressure increased significantly (p less than 0.001) in both the cardiomyopathic and the normal hamster heart despite concomitant reduction in myocardial flow rate favoring a direct inotropic effect of Ang I in both normal and myopathic hearts; these changes were significantly higher by almost threefold in the cardiomyopathic than in the normal hamsters (p less than 0.01) and were blocked by the angiotensin II (Ang II) antagonist [Sar1,Thr8]Ang II. Comparing dose-left ventricular contractility response curves for Ang I and Ang II, ED50 for responses was identical in both normal and myopathic hearts, whereas peak responses to Ang II were double those to Ang I in normal hearts but were almost identical in the myopathic hearts. Binding of [125I]Ang II in six cardiomyopathic and four normal hamster hearts was of high affinity, but there was no evidence for Ang I-saturable high-affinity binding sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Angiotensin I; Angiotensin II; Angiotensin Receptor Antagonists; Angiotensins; Animals; Captopril; Cardiac Output, Low; Cardiomyopathies; Cricetinae; Drug Synergism; Heart; Male; Mesocricetus; Myocardial Contraction; Myocardium; Receptors, Angiotensin