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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Inhibitors of two zinc metallopeptidases, angiotensin I converting enzyme (ACE) and neutral metalloendopeptidase-24.11 (EP-24.11), are antihypertensive agents. In this issue of Hypertension, Genden and Molineaux report that yet another peptidase inhibitor, metalloendopeptidase-24.15, EC 3.4.24.15 (EP-24.15), lowers blood pressure in normotensive rats. In this editorial we discuss the possible role of kinins as common mediators of part of the vasodepressor action of these peptidase inhibitors. Genden and Molineaux report that the marked fall in blood pressure caused by the EP-24.15 inhibitor is almost abolished by a kinin receptor antagonist, supporting the hypothesis that kinins play a role in the regulation of normal blood pressure. We have confirmed that the EP-24.15 inhibitor used by these investigators lowers blood pressure. Up to now, EP-24.15 has not been implicated in in vivo metabolism of kinins. Although a number of kininases have been identified, our own previous work indicated that the metabolic pathway responsible for clearing kinins from the circulation involves the action of kininase II (angiotensin I converting enzyme) and renal peptidases. Nevertheless, the main metabolic pathway involved some other unidentified enzyme, since in these experiments disappearance of kinins from the circulation was only marginally reduced by a "cocktail" of inhibitors of ACE, EP-24.11, and carboxypeptidase N. It could be that EP-24.15 is involved in kinin metabolism. However, a number of questions need to be answered with regard to the mechanism by which the EP-24.15 inhibitor lowers blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)
Hypertension 1991 Sep
PMID:Zinc metallopeptidase inhibitors. A novel antihypertensive treatment. 188 49

This study was undertaken to verify the activity of plasma kininases in hypertension. Male Wistar rats (WIS) were used and three models of experimental hypertension were studied: spontaneously hypertensive rats (SHR), renal hypertensive rats, made according to the method of Goldblatt, DOCA-salt hypertensive rats. Normal Wistar rats, nephrectomized rats and sodium-loaded rats were used as control groups. Plasma from these animals was used to evaluate the kininase activities: kininase II activity (KII) was measured by the hydrolysis of hippuryl-L-histidyl-L-leucine (HHL); kininase I activity (KI) was measured by the hydrolysis of hippuryl-L-arginine (HLA) (CN1 activity) and of hippuryl-L-lysine (HLL) (CN2 activity). The three enzyme activities were characterized by their kinetic constants and the inhibitory pattern of various inhibitors. In normal WIS rats, hydrolysis of HHL proceeds with a Km of 2.55 +/- 0.22 mM and at a Vmax of 0.357 +/- 0.017 mumol/min/ml; the enzyme is inhibited by EDTA, 0-phenanthroline and captopril. HLA has a Km of 6.93 +/- 0.32 mM and a Vmax of 0.748 +/- 0.019 mumol/min/ml while the Km and Vmax values of HLL are 35.8 +/- 1.52 mM and 13.11 +/- 0.40 mumol/min/ml. The hydrolysis of both substrates is inhibited by EDTA, 0-phenanthroline and MERGETPA. KII activity is decreased in WKY and SHR rats (Vmax = 0.241 +/- 0.014 and 0.262 +/- 0.011 mumol/min/ml, respectively). In renal hypertensive rats and DOCA-salt hypertensive rats, the KII activity remained unchanged. CN1 activity was increased in 1K, 1C hypertensive animals (Vmax = 0.866 +/- 0.221 mumol/min/ml) and in DOCA-salt hypertensive rats (Vmax = 1.119 +/- 0.049 mumol/min/ml).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Activity of plasma kininase I and kininase II in hypertensive rats]. 217 85

The importance of kininase I (carboxypeptidase N) in the catabolism of circulating kinins is not known. DL-2-Mercaptomethyl-3-guanidinoethylthiopropanoic acid (MGTA) has been reported to be an inhibitor of kininase I both in vitro and in vivo. In order to evaluate the possible role of kininase I in the in vivo inactivation of bradykinin, the authors studied the blood pressure responses of pentobarbital-anesthetized rats to bradykinin before and after the i.v. administration of MGTA (a 10-mg/kg bolus followed by 1 mg/kg/min continuous infusion). MGTA potentiated bradykinin-induced hypotension. The specificity of MGTA for kininase I was tested using other peptide and nonpeptide vasoactive substances. MGTA potentiated the hypertension due to angiotensin I, angiotensin II and vasopressin, but it did not affect the response to phenylephrine. On the other hand, MGTA did not potentiate the hypotensive action of acetylcholine, but it did potentiate that of sodium nitroprusside. The potentiation of bradykinin-induced hypotension is compatible with inhibition of kininase I by MGTA. The data suggest, however, that MGTA is not selective for any enzyme that inactivates kinins, inasmuch as other peptides and nonpeptide vasoactive substances are also potentiated.
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PMID:Effect of DL-2-mercaptomethyl-3-guanidinoethylthiopropanoic acid on the blood pressure response to vasoactive substances. 242 Sep 68

Arterial plasma kinins and mean arterial pressure were measured in intact and bilaterally nephrectomized rats infused with vehicle or bradykinin to study the role of 1) angiotensin converting enzyme (ACE) and other peptidases and 2) the kidney (a kininase-rich organ) in the metabolism of kinins in vivo. Before the infusion, rats were pretreated with vehicle, enalaprilat (an ACE inhibitor), or a cocktail of kininase inhibitors containing 1) enalaprilat, 2) DL-2-mercaptomethyl-3-guanidinoethyl-thiopropanoic acid (MGTA), a carboxypeptidase N inhibitor, 3) phosphoramidon, a neutral endopeptidase 24.11 inhibitor, and 4) bestatin, an aminopeptidase B inhibitor. In the rats with vehicle (n = 8), the cocktail did not significantly increase endogenous kinins (from 31 +/- 6 to 41 +/- 9 pg/ml, p = 0.94). In the rats infused with bradykinin (peptidase substrate), plasma kinins increased threefold in the group pretreated with the vehicle, 21-fold in the enalaprilat group, and 22-fold in the cocktail group. These increases were doubled by nephrectomy but were not affected by ureteral ligation. In the groups pretreated with the cocktail or enalaprilat, the hypotensive effect of bradykinin was correlated with plasma kinin concentration (r = 0.75, p less than 0.001). After bradykinin infusion was stopped, plasma kinins decreased by half in 10-12 seconds in the rats pretreated with vehicle, enalaprilat, or cocktail. We concluded that ACE and the kidney are important to the metabolism of circulating kinins while carboxypeptidase N, neutral endopeptidase 24.11 and aminopeptidase B are not. We also concluded that other tissue peptidases, not affected by either the above inhibitors or nephrectomy, play an important role in kinin metabolism.
Hypertension 1989 Sep
PMID:Role of angiotensin converting enzyme and other peptidases in in vivo metabolism of kinins. 254 61

The effects of 1, 10, or 40 micrograms/ml of vanadium, given for six or seven months as sodium metavanadate in drinking water on cardiovascular and biochemical variables and the electrolyte metabolism of male Sprague-Dawley rats were investigated. At the end of the exposure period, all animals exposed to vanadate had increased systolic and diastolic blood pressure. This effect was not dose dependent and heart rate and cardiac inotropism were not affected. The role of defective renal function and electrolyte metabolism in such effects was supported, in the rats exposed to 10 and 40 ppm of vanadium, by the following changes: (a) decreased Na, + K(+)-ATPase activity in the distal tubules of nephrons; (b) increased urinary excretion of potassium; (c) increase in plasma renin activity and urinary kallikrein, kininase I, and kininase II activities; (d) increased plasma aldosterone (only in the rats treated with 10 ppm of vanadium). The alterations in the rats exposed to 1 ppm of vanadium were: (a) reduced urinary calcium excretion; (b) reduced urinary kallikrein activity; (c) reduced plasma aldosterone. These results suggest that blood hypertension in rats exposed to vanadate depends on specific mechanisms of renal toxicity related to the levels of exposure.
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PMID:Renal toxicity and arterial hypertension in rats chronically exposed to vanadate. 804 51

To elucidate the significance of renal kininases in primary aldosteronism (PA), urinary total kininase, kininase I, II and neutral endopeptidase 24.11 (NEP) were examined and evaluated for the regulation mechanisms of these kininases. Total kininase, kininase I and NEP were significantly higher in PA than in normotensives (NT), whereas no difference was found for kininase II. Moreover, 42% of total kininase consisted of unknown kininase(s), different from kininase I, II or NEP. There were significantly positive correlations between plasma aldosterone concentration and total kininase, kininase I and unknown kininase(s) in PA. After the adrenalectomy, urinary kininases decreased into normal ranges, and unknown kininase(s) were negligible. These findings suggested that: 1) kininase I and NEP are accelerated in PA; 2) unknown kininase(s) differing from kininase I, II or NEP may exist in PA; 3) mineralocorticoids may regulate renal kininases; and 4) accelerated renal kininases may play some role in disorders of the renal water-sodium metabolism and in high blood pressure in PA.
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PMID:Significance of renal kininases in patients with primary aldosteronism. 855 3

To further clarify the significance of renal kininases in patients with Cushing's syndrome, daily urinary excretions of total kininase, kininase I, Ii and neutral endopeptidase 24.11 (NEP) were examined and evaluated for the relations between plasma cortisol level and these kininases. Urinary total kininase kininase I, II and NEP were significantly higher in patients with Cushing's syndrome than in normotensives. There was a significant positive correlation between plasma cortisol level and total kininase or NEP, and the same tendency was observed between plasma cortisol level and kininase I. After adrenalectomy, urinary kininases decreased to normal levels. These findings suggested that: 1) kininase I, II and NEP are accelerated in Cushing's syndrome; 2) glucocorticoids may regulate renal kininases; and 3) accelerated renal kininases may play some role in disorders of the renal water-sodium metabolism and in high blood pressure in Cushing's syndrome.
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PMID:Significance of renal kininases in patients with Cushing's syndrome. 856 95

Rats were exposed for 10 months to 60 ppm of Pb (as acetate) in drinking water. Systolic and diastolic blood pressure and cardiac inotropism were increased by the metal, which reduced arterial blood flow and unaffected heart rate. The activities of plasma angiotensin I-converting enzyme (ACE) and kininase II were strongly augmented by Pb, suggesting markedly increased and decreased levels of plasma angiotensin II and bradykinin, respectively. Moreover, the Pb-exposed rats showed a lower increase of the plasma kallikrein and kininase I activities. These results are discussed in the context of the complex relationships linking the renin-angiotensin-aldosterone (RAA), kallikrein-kinin and other autacoidal, neurohumoral (e.g., catecholaminergic) and transductional systems (e.g., nitric oxide (NO)). Pb was confirmed to induce arterial hypertension and cardiovascular alterations at plasma levels similar to those observed in the general population or in subjects with short occupational exposure.
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PMID:Kininergic system and arterial hypertension following chronic exposure to inorganic lead. 1060 32

Kinins are vasoactive peptide hormones that can confer protection against the development of hypertension. Because their efficacy is greatly influenced by the rate of enzymatic degradation, the activities of various kininases in plasma and blood of spontaneously hypertensive rats (SHR) were compared with those in normotensive Wistar-Kyoto rats (WKY) to identify pathogenic alterations. Either plasma or whole blood was incubated with bradykinin (10 microM). Bradykinin and kinin metabolites were measured by high-performance liquid chromatography. Kininase activities were determined by cumulative inhibition of angiotensin I-converting enzyme (ACE), carboxypeptidase N (CPN), and aminopeptidase P (APP), using selective inhibitors. Plasma of WKY rats degraded bradykinin at a rate of 13.3 +/- 0.94 micromol x min(-1) x l(-1). The enzymes ACE, APP, and CPN represented 92% of this kininase activity, with relative contributions of 52, 25, and 16%, respectively. Inclusion of blood cells at physiological concentrations did not extend the activities of these plasma kininases further. No differences of kinin degradation were found between WKY and SHR. The identical conditions of kinin degradation in WKY and SHR suggest no pathogenic role of kininases in the SHR model of genetic hypertension.
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PMID:Pathways of bradykinin degradation in blood and plasma of normotensive and hypertensive rats. 1129 20

Bradykinin is a small peptide that acts mainly as a hormone by activating specific receptors that confer protection against the development of hypertension. The efficacy of bradykinin is influenced by the activities of various kininases present in plasma and blood. In this study, both human and rat plasma were incubated with a labelled form of bradykinin (at 4 and 12.5 microM), that will be referred to as bromobradykinin. The metabolic fate of bromobradykinin was monitored by liquid chromatography coupled to an orthogonal acceleration time-of-flight mass spectrometer (oaTOF). Quantification measurements of the bromine-containing metabolites were performed on-line, via flow splitting, by inductively coupled plasma mass spectrometry (ICPMS). The data obtained highlighted that the mechanism(s) of bradykinin metabolism in human and rat plasma are different, with the metabolism of bradykinin in rat plasma being much more aggressive than that observed in human plasma. In addition to the known bradykinin metabolites, e.g. [1,5], [1,7] from ACE, [1,8] from carboxypeptidase and [2,9] from aminopeptidase activity, we have identified the presence of new bradykinin metabolites in both human and rat plasma. These have been identified as fragment [5], the amino acid phenylalanine, which was present in both the human and rat plasma and the fragments [2,8] and [4,8] in rat plasma. To our knowledge it is the first time that these fragments have been recorded in human and rat plasma. The occurrence of these new fragments provides evidence for the presence of potentially new enzymes and mechanisms of bradykinin metabolism. The method described here provides a powerful technique for monitoring the activity of the many kininases involved in bradykinin metabolism such as ACE (angiotensin I converting enzyme), carboxypeptidase N and aminopeptidase P. In addition, this procedure could be used as a screening assay for selecting and monitoring the actions of inhibitors of the enzymes implicated in bradykinin metabolism directly in plasma or serum.
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PMID:Study of bradykinin metabolism in human and rat plasma by liquid chromatography with inductively coupled plasma mass spectrometry and orthogonal acceleration time-of-flight mass spectrometry. 1180 44


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