angiotensin-i and Acute-Disease

The cumulative number of cases in the current global coronavirus disease 19 (COVID-19) pandemic, caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has exceeded 100 million, with the number of deaths caused by the infection having exceeded 2.5 million. Recent reports from most frontline researchers have revealed that SARS-CoV-2 can also cause fatal non-respiratory conditions, such as fatal cardiovascular events. One of the important mechanisms underlying the multiple organ damage that is now known to occur during the acute phase of SARS-CoV-2 infection is impairment of vascular function associated with inhibition of angiotensin-converting enzyme 2. To manage the risk of vascular dysfunction-related complications in patients with COVID-19, it would be pivotal to clearly elucidate the precise mechanisms by which SARS-CoV-2 infects endothelial cells to cause vascular dysfunction. In this review, we summarize the current state of knowledge about the mechanisms involved in the development of vascular dysfunction in the acute phase of COVID-19.

Topics: Acute Disease; Angiotensin I; Angiotensin-Converting Enzyme 2; Arteries; Cardiovascular Diseases; COVID-19; Humans; Morbidity; Peptide Fragments; Vascular Stiffness

Topics: Acute Disease; Adrenergic beta-Antagonists; Aged; Analgesics, Opioid; Angioplasty, Balloon, Coronary; Angiotensin I; Angiotensin Receptor Antagonists; Angiotensin-Converting Enzyme Inhibitors; Cardiac Glycosides; Defibrillators, Implantable; Diuretics; Emergencies; Furosemide; Heart Failure; Humans; Morphine; Myocardial Infarction; Nitrates; Nitroglycerin; Pacemaker, Artificial; Prognosis; Pulmonary Edema; Respiration, Artificial; Risk Factors; Shock, Cardiogenic; Time Factors; Vasodilator Agents; Ventricular Dysfunction, Right

Defective absorption of acute allergic airway inflammation is involved in the initiation and development of chronic asthma. After allergen exposure, there is a rapid recruitment of macrophages around the airways, which promote acute inflammatory responses. The Ang-(1-7)/Mas receptor axis reportedly plays protective roles in various tissue inflammation and remodeling processes in vivo. However, the exact role of Mas receptor and their underlying mechanisms during the pathology of acute allergic airway inflammation remains unclear.. We investigated the role of Mas receptor in acute allergic asthma and explored its underlying mechanisms in vitro, aiming to find critical molecules and signal pathways.. Mas receptor expression was assessed in ovalbumin (OVA)-induced acute asthmatic murine model. Then we estimated the anti-inflammatory role of Mas receptor in vivo and explored expressions of several known inflammatory cytokines as well as phosphorylation levels of MAPK pathways. Mas receptor functions and underlying mechanisms were studied further in the human bronchial epithelial cell line (16HBE).. Mas receptor expression decreased in acute allergic airway inflammation. Multiplex immunofluorescence co-localized Mas receptor and EpCAM, indicated that Mas receptor may function in the bronchial epithelium. Activating Mas receptor through AVE0991 significantly alleviated macrophage infiltration in airway inflammation, accompanied with down-regulation of CCL2 and phosphorylation levels of MAPK pathways. Further studies in 16HBE showed that AVE0991 pre-treatment inhibited LPS-induced or anisomycin-induced CCL2 increase and THP-1 macrophages migration via JNK pathways.. Our findings suggested that Mas receptor activation significantly attenuated CCL2 dependent macrophage recruitments in acute allergic airway inflammation through JNK pathways, which indicated that Mas receptor, CCL2 and phospho-JNK could be potential targets against allergic airway inflammation.

Topics: Acute Disease; Angiotensin I; Animals; Asthma; Chemokine CCL2; Cytokines; Imidazoles; Inflammation; Macrophage Activation; Macrophages; Male; MAP Kinase Signaling System; Mice; Mice, Inbred BALB C; Ovalbumin; Peptide Fragments; Phosphorylation; Proto-Oncogene Mas; Proto-Oncogene Proteins; Receptors, G-Protein-Coupled; Respiratory System

We propose renin angiotensin system (RAS) peptides are critical in wound reparative processes such as in acute respiratory distress syndrome (ARDS). Their role in predicting clinical outcomes in ARDS has been unexplored; thus, we used a targeted metabolomics approach to investigate them as potential predictors of outcomes.. Thirty-nine ARDS patients were enrolled within 24 hours of ARDS diagnosis. Plasma RAS peptide levels were quantified at study entry and 24, 48 and 72 hours using a liquid chromatography-mass spectrometry based metabolomics assay. RAS peptide concentrations were compared between survivors and non-survivors, and were correlated with clinical and pulmonary measures.. Angiotensin I (Ang-I or A(1-10)) levels were significantly higher in non-survivors at study entry and 72 hours. ARDS survival was associated with lower A(1-10) concentration (OR 0.36, 95% CI 0.18-0.72, p = 0.004) but higher A(1-9) concentration (OR 2.24, 95% CI 1.15-4.39, p = 0.018), a biologically active metabolite of A(1-10) and an agonist of angiotensin II receptor type 2. Survivors had significantly higher median A(1-9)/A(1-10) and A(1-7)/A(1-10) ratios than the non-survivors (p = 0.001). Increased A(1-9)/A(1-10) ratio suggests that angiotensin converting enzyme II (ACE2) activity is higher in patients who survived their ARDS insult while an increase in A(1-7)/A(1-10) ratio suggests that ACE activity is also higher in survivors.. A(1-10) accumulation and reduced A(1-9) concentration in the non-survivor group suggest that ACE2 activities may be reduced in patients succumbing to ARDS. Plasma levels of both A(1-10) and A(1-9) and their ratio may serve as useful biomarkers for prognosis in ARDS patients.

Topics: Acute Disease; Adult; Angiotensin I; Angiotensin-Converting Enzyme 2; Chromatography, High Pressure Liquid; Female; Humans; Male; Middle Aged; Peptides; Peptidyl-Dipeptidase A; Pilot Projects; Receptors, Angiotensin; Respiratory Distress Syndrome; Tandem Mass Spectrometry

The existence of a new cascade, angiotensin-converting enzyme (ACE) 2/angiotensin (Ang)-(1-7)/Mas receptor axis, has been recently established in the renin-angiotensin system. However, the dynamics of this cascade under various pathological conditions in clinical settings is still unclear. Forty-nine patients who underwent emergency hospitalization because of acute heart failure (AHF) consented to participate in this study. Thirty-eight healthy volunteers served as controls. Serum ACE activity, ACE2, Ang-(1-7) concentration, plasma Ang II, aldosterone concentration, and plasma renin activity (PRA) were measured at the acute stage. We conducted a comparative study between patients with AHF and healthy volunteers. Patients with AHF showed lower serum ACE activity and plasma aldosterone concentration than healthy volunteers (12.3 vs. 15.1 IU/L, respectively; P = 0.01, 75.6 vs. 125.3 pg/mL, respectively; P = 0.000); there were no differences between the two groups in PRA and plasma Ang II concentration. Patients with AHF had a higher serum ACE2 concentration than healthy volunteers (7.9 vs. 4.8 ng/mL, respectively; P = 0.002), but their serum Ang-(1-7) concentration was significantly lower (2.4 vs 3.1 ng/mL, respectively; P = 0.005). Patients with AHF had a higher serum ACE2 concentration, lower serum Ang-(1-7) concentration, and lower serum ACE activity and plasma aldosterone concentrations than healthy volunteers, whereas PRA and plasma Ang II concentration were the same.

Topics: Acute Disease; Adult; Aged; Aldosterone; Angiotensin I; Angiotensin II; Angiotensin-Converting Enzyme 2; Blood Pressure; Case-Control Studies; Emergencies; Female; Heart Failure; Hospitalization; Humans; Japan; Male; Middle Aged; Peptide Fragments; Peptidyl-Dipeptidase A; Regression Analysis; Renin; Renin-Angiotensin System

To investigate the effects of the angiotensin-(1-7) signaling pathway and the possible role of atrial natriuretic peptide (ANP) on atrial electrical remodeling in canines with acute atrial tachycardia.. Forty dogs were randomly assigned to eight groups (five dogs/group): sham, paced control, paced + angiotensin-(1-7), paced + angiotensin-(1-7) + Mas inhibitor, paced + angiotensin-(1-7) + Akt inhibitor, paced + angiotensin-(1-7) + PI3K inhibitor, paced + angiotensin-(1-7) + nitric oxide (NO) inhibitor, and paced + angiotensin-(1-7) + A-71915 (ANP receptor antagonist). Rapid atrial pacing was maintained at 600 bpm for 2 h for all groups, except the sham group, and angiotensin-(1-7) (6 μg kg(-1) h(-1)), Mas inhibitor (5.83 μg kg(-1) h(-1)), Akt inhibitor (2.14 μg kg(-1) h(-1)), PI3K inhibitor (2.86 μg kg(-1) h(-1)), NO synthase inhibitor (180 μg kg(-1)h(-1)), or A-71915 (0.30 μg kg(-1) h(-1)) were administered intravenously. Atrial effective refractory periods, inducibility, and duration of atrial fibrillation (pacing cycle lengths: 300, 250, and 200 ms), and left atrial ANP concentrations were measured.. After pacing, the atrial effective refractory periods at the six sites shortened with increased inducibility and duration of atrial fibrillation, which was attenuated by angiotensin-(1-7), and increased ANP concentrations, which was promoted by angiotensin-(1-7) (paced control vs. sham; P < 0.05). All inhibitors and A-71915 blocked the electrophysiological effects of angiotensin-(1-7). ANP secretion induced by angiotensin-(1-7) was also blocked by all inhibitors.. Angiotensin-(1-7) prevented acute electrical remodeling in canines with acute atrial tachycardia via the angiotensin-(1-7)/Mas/PI3K/Akt/NO signaling pathway. ANP was related to the anti-arrhythmic effects of angiotensin-(1-7).

Topics: Acute Disease; Angiotensin I; Animals; Atrial Fibrillation; Atrial Natriuretic Factor; Disease Models, Animal; Dogs; Heart Atria; Hemodynamics; Nitric Oxide; Peptide Fragments; Phosphatidylinositol 3-Kinases; Proto-Oncogene Mas; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Receptors, G-Protein-Coupled; Refractory Period, Electrophysiological; Signal Transduction; Tachycardia; Time Factors

Angiotensin-converting enzyme (ACE) and its effector peptide angiotensin II (Ang II) have been implicated in the pathogenesis of pancreatitis. Angiotensin-converting enzyme 2 (ACE2) degrades Ang II to angiotensin-(1-7) [Ang-(1-7)] and has recently been described to have an antagonistic effect on ACE signalling. However, the specific underlying role of ACE2 in the pathogenesis of severe acute pancreatitis (SAP) is unclear. In the present study, the local imbalance of ACE and ACE2, as well as Ang II and Ang-(1-7) expression, was compared in wild-type (WT) and ACE2 knock-out (KO) or ACE2 transgenic (TG) mice subjected to cerulein-induced SAP. Serum amylase, tumour necrosis factor-α, interleukin (IL)-1β, IL-6 and IL-10 levels and histological morphometry were used to determine the severity of pancreatitis. In WT mice, pancreatic ACE and Ang II and serum Ang II expression increased (P < 0.05), while pancreatic ACE2 and Ang-(1-7) and serum Ang-(1-7) levels were also significantly elevated (P < 0.05) from 2 to 72 h after the onset of SAP. However, the ratio of pancreatic ACE2 to ACE expression was significantly reduced (from 1.46 ± 0.09 to 0.27 ± 0.05, P < 0.001) and paralleled the severity of pancreatitis. The Ace2 KO mice exhibited increased levels of tumour necrosis factor-α, IL-1β, IL-6, multifocal coagulative necrosis and inflammatory infiltrate, and lower levels of serum IL-10 and pancreatic Ang-(1-7) (4.70 ± 2.13 versus 10.87 ± 2.51, P < 0.001) compared with cerulein-treated WT mice at the same time point. Conversely, Ace2 TG mice with normal ACE expression were more resistant to SAP challenge as evidenced by a decreased inflammatory response, attenuated pathological changes and increased survival rates. These data suggest that the ACE2-ACE imbalance plays an important role in the pathogenesis of SAP and that pancreatic ACE2 is an important factor in determining the severity of SAP.

Topics: Acute Disease; Amylases; Angiotensin I; Angiotensin II; Angiotensin-Converting Enzyme 2; Animals; Biomarkers; Ceruletide; Disease Models, Animal; Genotype; Inflammation Mediators; Male; Mice, Inbred C57BL; Mice, Knockout; Necrosis; Pancreas; Pancreatitis; Peptide Fragments; Peptidyl-Dipeptidase A; Phenotype; Severity of Illness Index; Time Factors

Ulinastatin is a drug used effectively to alleviate symptoms and improve the pathophysiology of various types of pancreatitis. However, the molecular mechanism responsible for its action remains unknown. Therefore, we further explore the therapeutic effects of ulinastatin and investigate possible molecular pathways modulated by this drug in the development of severe acute pancreatitis (SAP).. SAP mouse model was created by administering intraperitoneal injections of cerulein and lipopolysaccharide. Pancreatic injury was assessed by performing biochemical and histological assays and by measuring the inflammatory response of the pancreas. Specifically, we examined changes in the expression of components of the rennin-angiotensin system (RAS), including angiotensin-converting enzyme (ACE)-angiotensin II (Ang II)-angiotensin type 1 receptor (AT-1R), and ACE2-Ang-(1-7)-Mas receptor.. When SAP mouse models were treated with ulinastatin at a dosage of 50,000 U/kg body weight, we found, through biochemical and histopathological analyses, that the pancreatic injury was significantly ameliorated. Administration of ulinastatin to SAP mice led to increased expression of ACE2, Ang-(1-7), and Mas receptor, decreased expression of serum Ang II and pancreatic AT-1R, and no alterations in the expression of pancreatic ACE and Ang II when compared to cerulein-treated control group that did not receive ulinastatin.. This study shows that ulinastatin has differential effects on the two axes of the RAS during SAP. Our results further suggest that upregulation of components of the ACE2-Ang-(1-7)-Mas pathway might be an important mechanism contributing to the therapeutic role of ulinastatin in alleviating pancreatitis-associated symptoms.

Topics: Acute Disease; Angiotensin I; Angiotensin II; Angiotensin-Converting Enzyme 2; Animals; Ceruletide; Disease Models, Animal; Gene Expression; Glycoproteins; Lipopolysaccharides; Mice, Inbred C57BL; Molecular Targeted Therapy; Pancreatitis; Peptide Fragments; Peptidyl-Dipeptidase A; Prospective Studies; Receptor, Angiotensin, Type 1; Renin-Angiotensin System; Severity of Illness Index

There is now unequivocal evidence that the angiotensin-converting enzyme 2(ACE2)-Ang-(1-7)-Mas axis is a key component of the renin-angiotensin system (RAS) cascade, which is closely correlated with ischemic insult occurrence. Our previous studies demonstrated that the Ang-(1-7), was an active member of the brain RAS. However, the ACE2-Ang-(1-7)-Mas axis expression after cerebral ischemic injury are currently unclear. In the present study, we investigated the time course of ACE2-Ang-(1-7) and Mas receptor expression in the acute stage of cerebral ischemic stroke. The content of Ang-(1-7) in ischemic tissues and blood serum was measured by specific EIA kits. Real-time PCR and western blot were used to determine messenger RNA (mRNA) and protein levels of the ACE2 and Mas. The cerebral ischemic lesion resulted in a significant increase of regional cerebral and circulating Ang-(1-7) at 6-48 h compared with sham operation group following focal ischemic stroke (12h: 7.276±0.320 ng/ml vs. 2.466±0.410 ng/ml, serum; 1.024±0.056 ng/mg vs. 0.499±0.032, brain) (P<0.05). Both ACE2 and Mas expression were markedly enhanced compared to the control in the ischemic tissues (P<0.05). Mas immunopositive neurons were also seen stronger expression in the ischemic cortex (19.167±2.858 vs. 7.833±2.483) (P<0.05). The evidence collected in our present study will indicate that, ACE2-Ang-(1-7)-Mas axis are upregulated after acute ischemic stroke and would play a pivotal role in the regulation of acute neuron injury in ischemic cerebrovascular diseases.

Topics: Acute Disease; Angiotensin I; Angiotensin-Converting Enzyme 2; Animals; Brain Ischemia; Cerebral Cortex; Infarction, Middle Cerebral Artery; Male; Peptide Fragments; Peptidyl-Dipeptidase A; Proto-Oncogene Mas; Proto-Oncogene Proteins; Rats; Rats, Sprague-Dawley; Receptors, G-Protein-Coupled; Stroke; Up-Regulation

This study investigated whether adenosine mediates the decrease in plasma renin activity (PRA) during acute hypoxia. Eight chronically tracheotomized, conscious beagle dogs were kept under standardized environmental conditions and received a low-sodium diet (0.5 mmol.kg body wt(-1).day(-1)). During the experiments, the dogs were breathing spontaneously via a ventilator circuit: first hour, normoxia (21% inspiratory concentration of O(2)); second and third hours, hypoxia (10% inspiratory concentration of O(2)). Each of the eight dogs was studied twice in randomized order in control and theophylline experiments. In theophylline experiments, theophylline, an A(1)-receptor antagonist, was infused intravenously during hypoxia (loading dose: 3 mg/kg within 30 min, maintenance: 0.5 mg. kg(-1). h(-1)). In theophylline experiments, PRA (5.9 +/- 0.8 ng ANG I. ml(-1). h(-1)) and ANG II plasma concentration (15.9 +/- 2.3 pg/ml) did not decrease during hypoxia, whereas plasma aldosterone concentration decreased from 277 +/- 63 to 132 +/- 23 pg/ml (P < 0.05). In control experiments, PRA decreased from 6.8 +/- 0.8 during normoxia to 3.0 +/- 0.5 ng ANG I. ml(-1). h(-1) during hypoxia, ANG II decreased from 13.3 +/- 1.9 to 7.3 +/- 1.9 pg/ml, and plasma aldosterone concentration decreased from 316 +/- 50 to 70 +/- 13 pg/ml (P < 0.05). Thus infusion of the adenosine receptor antagonist theophylline inhibited the suppression of the renin-angiotensin system during acute hypoxia. The decrease in aldosterone occurred independently and is apparently directly related to hypoxia. In conclusion, it is likely that adenosine mediates the decrease in PRA during acute hypoxia in conscious dogs.

Topics: Acute Disease; Adenosine; Aldosterone; Angiotensin I; Angiotensin II; Animals; Blood Pressure; Carbon Dioxide; Consciousness; Diet, Sodium-Restricted; Dogs; Female; Heart Rate; Hemodynamics; Hypoxia; Oxygen; Partial Pressure; Potassium; Purinergic P1 Receptor Antagonists; Renin; Renin-Angiotensin System; Theophylline

Elevated cerebrospinal fluid (CSF) angiotensin I-converting enzyme (ACE) levels have been evidenced in patients with schizophrenia who have been treated with antipsychotics. In order to explore a possible mononuclear cell origin of CSF ACE, the authors determined CSF ACE and CSF mononuclear cell counts from 25 acutely psychotic patients, who had been drug-free for at least 4 months but started on conventional antipsychotic medication within a few days before sampling. No correlations were found between CSF to serum ACE ratio and CSF mononuclear cell counts. However, CSF total mononuclear cell count, CSF lymphocyte count, and CSF mononuclear phagocyte count evidenced significant positive correlations with current dose of antipsychotic medication expressed as chlorpromazine equivalents. The authors conclude that no indication of a relationship between mononuclear cells and CSF ACE activity was found. Surprisingly, a relationship between chlorpromazine dose and CSF mononuclear cell counts was found, which may indicate drug-related changes in cell-mediated immunity. This finding needs replication and further corroboration in well-designed studies.

Topics: Acute Disease; Adult; Angiotensin I; Antipsychotic Agents; Chlorpromazine; Cross-Sectional Studies; Dose-Response Relationship, Drug; Female; Haloperidol; Humans; Immunity, Cellular; Lymphocytes; Macrophages; Male; Middle Aged; Peptidyl-Dipeptidase A; Psychotic Disorders; Sampling Studies; Schizophrenia; Therapeutic Equivalency

-This study was designed to investigate distribution and regulation of the renal AT1A and AT2 subtype receptors in rats with either systemic angiotensin II (Ang II)-induced hypertension or acute phase renal hypertension (2-kidney, 1-clip [2K1C] or 2-kidney, 1-figure-of-8-wrap [2K1W]). In normal rat kidneys, positive immunostaining for the AT1A receptor was observed in the intrarenal vasculature, glomeruli, proximal and distal tubules, and collecting ducts. The AT2 receptor was localized mainly to the glomeruli. The AT1A but not AT2 receptor protein expression was significantly reduced in rats with 10-day systemic Ang II-induced hypertension. In both 7-day 2K1C and 3-day 2K1W rats, the AT1A receptor was significantly reduced in ischemic and contralateral kidneys compared with sham-operated control rats. Reduction in AT2 receptor expression was observed only in the ischemic kidneys in 2K1C and 2K1W renal hypertensive rats. These results demonstrate that the AT1A receptor is widely distributed in the glomerulus and all other nephron segments of the rat kidney. Renal AT1A but not AT2 receptor protein is downregulated in rats with Ang II-induced hypertension. In renal hypertensive rats, the AT1A receptor is bilaterally downregulated and the AT2 receptor is downregulated only in the ischemic kidney.

Topics: Acute Disease; Angiotensin I; Angiotensin II; Animals; Blotting, Western; Down-Regulation; Female; Gene Expression Regulation; Hypertension; Hypertension, Renal; Immunohistochemistry; Kidney; Kidney Glomerulus; Kidney Tubules; Rats; Rats, Sprague-Dawley; Receptors, Angiotensin

Angiotensinogen is the precursor of biologically active peptide angiotensin II and its hepatic synthesis is increased by the induction of acute inflammation. Studies were carried out to know whether the rise in plasma angiotensinogen is actually involved in the activity of the renin-angiotensin system during acute inflammation. The plasma level of angiotensinogen in rats was increased to 2.5 times the normal level 16 h after the induction of acute inflammation by administration of lipopolysaccharide (LPS). The plasma renin concentration (PRC) was decreased to about 40% of the normal level concomitantly with a reduction of plasma renin activity (PRA) at 4 h after LPS administration. In contrast, 16 h after LPS injection, when plasma angiotensinogen showed a high level and PRC had recovered to the normal range, PRA was increased to 1.7 times the normal level. These results indicate that acute inflammation induced by LPS causes a biphasic change in the generation of angiotensin I, i.e., an early decrease depending upon the reduction of PRC and later increase depending upon elevation of the angiotensinogen concentration.

Topics: Acute Disease; Angiotensin I; Angiotensinogen; Animals; Inflammation; Lipopolysaccharides; Male; Rats; Rats, Inbred F344; Renin; Renin-Angiotensin System

Enalapril, a new potent orally active angiotensin-converting enzyme inhibitor, was studied in cats subjected to acute myocardial ischemia. Enalapril, administered intravenously (2 mg/kg, plus 2 mg/kg/h) 30 min after ligation of the left coronary artery, significantly reduced the pressure-rate index, an indicator of myocardial oxygen demand. This was confirmed in isolated cat papillary muscles where enalapril reduced contractile force by 5-10%. During myocardial ischemia, enalapril reversed the elevated S-T segment of the electrocardiogram toward normal 2 h after the onset of ischemia. Moreover, enalapril significantly blunted the increases in circulating creatine kinase (CK) activity, as well as significantly prevented the loss in myocardial CK activity. These changes correlated with reduced myocardial loss of compounds containing free amino-nitrogen. Enalapril effectively acted as a converting enzyme inhibitor over the 5-hour course of the observation period. However, enalapril also acted as an angiotensin antagonist in isolated coronary arteries, a finding that may help explain its efficacy in myocardial ischemia. Enalapril did not appear to stabilize the membranes of cat liver lysosomes, and thus probably does not protect the ischemic myocardium by lysosomal stabilization.

Topics: Acute Disease; Angiotensin I; Angiotensin-Converting Enzyme Inhibitors; Animals; Blood Pressure; Cats; Coronary Circulation; Coronary Disease; Creatine Kinase; Dipeptides; Electrocardiography; Enalapril; Male; Oligopeptides; Papillary Muscles; Teprotide

The brain oedema, distribution space (DS) and brain uptake index (BUI), of L-glucose, inulin, B12 vitamin and of three polypeptidic hormones of increasing molecular weight (angiotensin-I, gastrin and insulin) were measured in the rat after sham operation, porto-caval shunt (PCS) or liver ischaemia. At an early stage following PCS or liver ischaemia brain oedema was not constant, and was only demonstrable after liver ischaemia in a large number of animals. Substances without an active transport and with a low diffusion coefficient such as L-glucose and inulin had a very low BUI, unchanged even if the 3H2O brain content or the DS were modified. B12 vitamin, DS and BUI were very high and did not change after liver ischaemia or PCS. Insulin DS and BUI were low in the three groups of animals, whereas it decreased after PCS for gastrin. A significant increase of BUI and DS (without any cerebral oedema) was demonstrated for angiotensin-I, a polypeptidic hormone of molecular weight 1300. This polypeptidic marker is in the same range of MW as the preliminary recently recognized medium-sized molecules which may be involved in the pathogenesis of encephalopathy during experimental acute liver failure. However, not only the MW, but the nature of such polypeptides may be of importance in the genesis of this limited impairment of BBB permeability.

Topics: Acute Disease; Angiotensin I; Animals; Blood-Brain Barrier; Brain Edema; Ischemia; Liver; Male; Molecular Weight; Permeability; Portacaval Shunt, Surgical; Rats; Rats, Inbred Strains; Vitamin B 12

We studied the effect of acute hypoxia on pulmonary conversion of angiotensin I to II in anesthetized dogs. When arterial PO2 was decreased from 86 +/- 14 (SD) to 33 +/- 8 mm Hg without changing pH or PCO2, the single passage conversion of intravenous boluses of radiolabeled angiotensin I in tracer doses fell significantly (P less than 0.005) from 72 +/- 4 to 67 +/- 6%. The effect of comparable levels of hypoxemia on the conversion of continuous intravenous infusions of pharmacological doses (1000 times physiological) of angiotensin I was greater: from 55 +/- 14 to 33 +/- 13% (P less than 0.025). There was prompt return of percent conversion ratios to control levels when hypoxemia was reversed. We conclude that acute hypoxia is associated with a reversible decrease in pulmonary angiotensin converting enzyme availability.

Topics: Acute Disease; Angiotensin I; Angiotensin II; Angiotensins; Animals; Blood Pressure; Carbon Dioxide; Cardiac Output; Dogs; Hydrogen-Ion Concentration; Hypoxia; Injections, Intravenous; Lung; Oxygen; Time Factors; Vasoconstriction

To determine if angiotension converting enzyme activity is altered by acute pathophysiological insults, we assessed angiotensin I conversion using a blood pressure response technique in anesthetized dogs studied during acute 100% O2 breathing and acute acid-base derangements. Also, we determined systemic vascular reactivity to angiotensin II by measuring the magnitude and duration of the arterial blood pressure response to intra-arterial injections of angiotensin II under these same conditions. Angiotensin I conversion found in normoxia [91 +/- 7 (SD)%] was unchanged by acute acidosis, alkalosis, and hyperoxia. During acute hyperoxia the mean half time of the hypertensive response increased from 68 +/- 25 (SD) s at a PaO2 of 112 +/- 18 (SD) Torr to 100 +/- 34 (SD) s at a PaO2 of 491 +/- 47 (SD) Torr (P less than 0.01). No other pathophysiological condition studied had any effect on reactivity of systemic vasculature to angiotensin II. We conclude that, except during acute hypoxia as previously shown, converting enzyme activity is resistant to other pathophysiological insults and that vascular responsiveness to angiotensin II is enhanced by hyperoxia.

Topics: Acid-Base Imbalance; Acidosis; Acidosis, Respiratory; Acute Disease; Alkalosis; Alkalosis, Respiratory; Angiotensin I; Angiotensin II; Angiotensins; Animals; Dogs; Hypoxia; Vascular Resistance