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Results for “Angiotensin-Converting Enzyme Inhibitors”

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PubMed1979

Long-term effects of captopril (SQ14 225) on blood-pressure and hormone levels in essential hypertension.

Captopril, an orally active angiotensin-converting enzyme (ACE) inhibitor, was effective in the long-term reduction of blood-pressure in 17 patients with essential hypertension. The addition of hydrochlorothiazide produced a further hypotensive effect, and the combined treatment produced satisfactory control of the blood-pressure for eight months. Captopril prevented and reversed the secondary hyperaldosteronism and hypokalaemia induced by simultaneous diuretic administration, thus eliminating the need for potassium supplements. The fall in plasma-angiotensin-II and urinary aldosterone and rise in angiotensin I and plasma-renin provide biochemical evidence that captopril inhibits ACE in vivo. No change in circulating venous bradykinin levels could be detected. The hypotensive action of captopril is not mediated by changes in blood-bradykinin but may involve inhibition of the renin-angiotensin and kallikrein-kinin systems locally within the kidneys or blood vessels.

Adult↗
PubMed1979

Improvement of chronic congestive heart-failure by oral captopril.

Catopril, an inhibitor of angiotensin converting enzyme, was given orally during cardiac catheterisation to 6 normotensive patients with refractory congestive heart-failure. 60--180 minutes after administration of 25 mg captopril, arterial pressure fell by 25%, cardiac index rose by 38%, and left-ventricular pressure and right-atrial pressure fell by 25% and 40% respectively. Plasma-renin activity rose while plasma noradrenaline and aldosterone fell. These data suggest that, in the short term, captopril can reduce both preload and afterload, and improve cardiac function, in refractory congestive heart-failure.

Administration, Oral↗
PubMed1976

Markedly elevated angiotensin converting enzyme in lymph nodes containing non-necrotizing granulomas in sarcoidosis.

Sarcoidosis is a disease of unknown etiology that is characterized by the generalized formation of granulomas and is accompanied by elevation in the serum in less than half the patients of angiotensin converting enzyme, a dipeptidyl carboxypeptidase that catalyzes the conversion of the decapeptide, angiotensin I, to the pressor octapeptide, angiotensin II, and L-histidyl-L-leucine. Mean activity of angiotensin converting enzyme was elevated generally more than 10-fold in granuloma-containing lymph nodes, but not in lung in which normally it is abundant, in 19 of 20 patients with sarcoidosis. Angiotensin converting enzyme in lymph nodes from subjects with sarcoidosis was similar to the enzyme from normal lung and lymph node with respect to activity as a function of pH, inhibition of activity by EDTA and o-phenanthroline, gel filtration on Sephadex G-200, and requirement for chloride for activity, but appeared to be more heat labile. The data suggest that the granulomas in sarcoidosis may be the source of the elevated serum enzyme and that cells of the granulomas, particularly the epitheloid cells which appear by electron microscopy to have active protein biosynthesis, may be actively synthesizing the enzyme.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1979

Converting-enzyme activity and pressor responses to angiotensin I and II in the rat awake and during anesthesia.

Plasma renin activity (rate of angiotensin I generation) does not increase during anesthesia with ketamine, fluroxene, halothane or enflurane in the sodium-repleted rat. However, blood pressure decreases when an angiotensin II antagonist, saralasin, is administered during halothane or enflurane anesthesia, but not during ketamine or fluroxene anesthesia. Differences in the rates of conversion of angiotensin I to angiotensin II induced by various anesthetic agents could help explain these previous findings. To determine the effects of anesthetic agents on angiotensin I conversion, experiments were performed in vitro and in vivo. The activities of rabbit pulmonary converting enzyme in the presence and absence of halothane or fluroxene were measured as rates of appearance of the dipeptide, histidyl-leucine, a product of angiotensin I hydrolysis to angiotensin II. Halothane and fluroxene did not alter conversion. Infusions of angiotensin I and angiotensin II were given to Wistar rats to construct dose-blood pressure response curves. The animals were then anesthetized with ketamine or halothane and infusions were repeated. Angiotensin I and angiotensin II induced similar blood pressure responses in awake and anesthetized rats. However, ketamine accentuated the pressor responses to angiotensin I and angiotensin II, whereas halothane depressed the responses. With the anesthetic agents studied, there is no significant effect on conversion of angiotensin I to angiotensin II either in vitro or in vivo.

Angiotensin I↗
PubMedDate not supplied

Equine angiotensin converting enzyme: a zinc metalloenzyme.

1. Angiotensin I converting enzyme from horse plasma has been extensively purified and shown to be homogeneous by disc-gel electrophoresis. 2. The metal ion involved in the catalytic reaction of the enzyme has been identified for the first time as zinc by atomic absorption spectrometry. 3. A number of other physicochemical properties of the enzyme are described and compared with results obtained by other investigators. The molecular weight was determined by gel filtration to be 113 000 daltons. The pH maximum was found to be 7-4. The chloride activation of the enzyme appears to act by facilitation of substrate binding to the enzyme. 4. By use of enzyme inhibitors, tyrosine has been implicated as a functional residue at the active site of the enzyme. 5. The enzyme shows a fairly high degree of specificity towards its substrates.

Angiotensin II↗
PubMed1975

Effect of inhibition of peptidase activity on distribution of intrarenal blood flow.

Experiments were performed in dogs to determine the effects of the intravenous administration of the dipeptide hydrolase inhibitor SQ 20,881 on renal hemodynamics, intrarenal blood flow distribution, and renal function. Dipeptide hydrolase converts angiotensin I to angiotensin II and inactivates bradykinin. SQ 20,881 causes an inhibition of the vasoconstrictor response after angiotensin I and potentiation of the vasodilatory activity of bradykinin. Total renal blood flow, cortical distribution of blood flow, and glomerular filtration rate were determined. In seven animals administration of SQ 20,881 (1 mg/kg) resulted in a decrease in mean systemic blood pressure of 11 mmHg, an increase in total renal blood flow of 0.71 ml/min per g, and a significant fall in glomerular filtration rate. Fractional blood flow to the superficial cortex decreased and to the juxtamedullary cortex increased. Absolute flow was unchanged in the superficial cortex and increased significantly in the deep cortex. The findings are compatible with reported effects of bradykinin on intrarenal blood flow distribution, although the experiments do not distinguish between potentiation of bradykinin or inhibition of angiotensin I conversion.

Angiotensin II↗
PubMed1975

Angiotensin and the hemodynamics of chronic salt deprivation.

Salt deprivation has been shown to cause fluid volume contraction and marked renin release; it is not clear whether angiotensin-induced vasoconstriction adds to low volume in compromising circulatory function or whether there are additional facets to the salt-deprived state. Mature Wistar rats were fed a low-salt diet for 1 mo and then, under pentobarbital anesthesia, compared to normals. Arterial pressure (is congruent to 125 mmHg), cardiac output (is congruent to 200 ml/min per kg), and total peripheral resistance were nearly identical in both groups. The influence of angiotensin was estimated by injecting converting enzyme inhibitor (SQ 20881, 1 mg/kg), and then observing the immediate hemodynamic response. Salt-deprived rats responded with a large (-47 mmHg) fall in pressure and total peripheral resistance indicating that, although total peripheral resistance was normal in salt deprivation, an increased fraction (30% vs. 11%) of the resistance was supported by angiotensin. Cardiac output decreased (-8%) in contrast to the increase that would be expected during marked arterial dilation; elevated angiotensin levels may have caused a moderate, beneficial decrease in venous compliance. These results suggest that circulatory function is adequately maintained during salt deprivation by a combination of normal total peripheral resistance and decreased venous compliance.

Angiotensin II↗
PubMed1976

Response to angiotensins I and II and to AI-converting-enzyme inhibitor in a shark.

The spiny dogfish shark, which does not have renal juxtaglomerular cells, exhibits a strong pressor response to both angiotensin I and II. A nonapeptide, angiotensin I-converting-enzyme inhibitor, blocks the pressor response to angiotensin I in this fish. The pressor response to both angiotensin II and norepinephrine is completely blocked by the adrenergic blocking drug phentolamine.

Adrenergic alpha-Antagonists↗
PubMed1975

Differentiation of nephrotensin from the renin angiotensin system.

An investigation of the relationship between nephrotensin and the renin angiotensin system was carred out. Nephrotensin was found in the plasma of rats with renal clip hypertension and with chemically induced kidney damage. There was no demonstrable correlation between presence of nephrotensin and plasma renin activity, and the pressor activity of nephrotensin was not altered by previous immunization of test animals with angiotensin II nor by pretreatment with angiotensin I converting enzyme inhibitor. These results indicate that nephrotensin is different from the components of the renin-angiotensin system.

Angiotensin II↗
PubMedDate not supplied

[Determination of carboxycathepsin (peptidyl dipeptidase) activity in human blood serum].

Based on fluorometric determination of a dipeptide histidil-leucine, which is splitted off from a synthetic substrate (Cbz-Phe-His-Leu) by carboxycathepsin (carboxydipeptidyl peptide hydrolase), a method was developed for estimation of the enzymatic activity in human blood serum. The method is characterized by simplicity and high sensitivity; Use of small amount of blood serum (about 0.03 ml) was possible. In normal human blood serum the carboxycathepsin activity varied from 7.5 to 18 nmoles of the dipeptide, liberated per mg of protein per hr.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1975

Prevention of pulmonary vascular changes of chronic alveolar hypoxia by inhibition of angiotensin I-converting enzyme in the rat.

To test the hypothesis that the renin-angiotensin system is involved in the development of the pulmonary vascular patholigic changes of chronic alveolar hypoxia, two groups of rats were exposed to 0.5 atm. for 21 days. One group received SQ 20,881 (2 mg. per kg.) every 8 hours subcutaneously and the second group received normal saline. A third group of rats was maintained at normobaria. Rats receiving SQ 20,881 had significantly less pulmonary arterial hypertrophy and right ventricular hypertrophy than hypobaric animals. SQ 20,881-treated rats showed a significant increase in adrenal weight but a marked reduction in the thickness of the zona glomerulosa, as compared with the other groups. Our findings indicate that angiotensin II is necessary in the development of the pulmonary vascular structural changes of chronic alveolar hypoxia.

Adrenal Glands↗
PubMed2025

Spike protein-induced VSIR-ISX signaling disrupts metabolic homeostasis and promotes COVID-19-related immune dysfunction.

COVID-19 has caused millions of deaths worldwide since 2019. Vaccination has reduced both transmission and disease severity. However, emerging viral variants have weakened vaccine effectiveness, highlighting the need for new antiviral therapies. This study examines how the SARS-CoV-2-Spike protein (SARS-2-S) induces the VSIR-ISX signaling pathway, leading to metabolic disturbances that may worsen disease progression. Using RNA sequencing, we found that SARS-2-S expression in pulmonary cells activates genes involved in tryptophan and arachidonic acid (AA) metabolism, altering bioactive mediators like kynurenine and prostanoids, which are crucial for inflammation and immune responses. Mechanistically, the ACE2-MYD88 pathway, activated by SARS-2-S, enhances the VSIR-ISX axis through NF-κB signaling, driving these metabolic disruptions. Chromatin immunoprecipitation and genome sequencing revealed that ISX, activated via VSIR-MAPK signaling, upregulates enzymes involved in AA metabolism by binding directly to their gene promoters. Notably, disrupting the VSIR-ISX axis using shRNA interference or NF-κB inhibitors effectively mitigated these metabolic disturbances. Our findings suggest that the VSIR-ISX pathway could be a promising therapeutic target for treating COVID-19 by addressing virus-induced metabolic disruptions.

Humans↗