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Biomedical subjects

J Ménard

Publications and source records attributed to J Ménard.

At least 289 records · Page 16Linked to original sources
PubMedDate not supplied

Local angiotensin II generation in the rat heart: role of renin uptake.

To elucidate the local effects of renin in the coronary circulation, we examined local angiotensin (Ang) I and II formation, as well as coronary vasoconstriction in response to renin administration, and compared the effects with exogenous infused Ang I. We perfused isolated hearts from rats overexpressing the human angiotensinogen gene in a Langendorff preparation and measured the hemodynamic effects and the released products. We also investigated cardiac Ang I conversion, including the contribution of non-angiotensin-converting enzyme-dependent Ang II-generating pathways. Finally, we studied Ang I conversion in vitro in heart homogenates. Renin and Ang I infusion both generated Ang II. Ang II release and vasoconstriction continued after renin infusion was stopped, even though renin disappeared immediately from the perfusate. In contrast, after Ang I infusion, Ang II release and coronary flow returned to basal levels. Ang I conversion (Ang II/Ang I ratio) was higher after renin infusion (0.109+/-0.027 versus 0.026+/-0.003, 15 minutes, P<.02) compared with infused Ang I. Remikiren added to the renin infusion abolished Ang I and II; captopril suppressed only Ang II, whereas an AT1 receptor blocker did not affect Ang I and II formation. All the drugs prevented renin-induced coronary flow changes. Total cardiac Ang II-forming activity was only partially inhibited by cilazaprilat (4.1+/-0.1 fmol x min(-1) x mg[-1]) and on a larger extent by chymostatin (2.6+/-0.3 fmol x min(-1) x mg[-1]) compared with control values (5.6+/-0.4 fmol x min(-1) x mg[-1]). We conclude that renin can be taken up by cardiac or coronary vascular tissue and induces long-lasting local Ang II generation and vasoconstriction. Locally formed Ang I was converted more effectively than infused Ang I. Furthermore, the comparison of in vivo and in vitro Ang I conversion suggests that in vitro assays may underestimate the functional contribution of angiotensin-converting enzyme to intracardiac Ang II formation.

Angiotensin I↗
PubMedDate not supplied

Cost-effectiveness of hypertension treatment.

The benefits of antihypertensive treatment are influenced by both the absolute initial cardiovascular risk, and the relative reduction. Because age is a major determinant of the absolute cardiovascular risk, and because the strategies for hypertension diagnosis and treatment are not very much influenced by age, hypertension management appears to be more cost-effective after the age of 45, in both men and women. Below this age, the absolute gain in life-years seems to be smaller, and sensitivity analysis demonstrate an important influence on the results of assumptions about the effects of treatment on quality of life and the discounting rate.

Adult↗
PubMedDate not supplied

Pharmacological demonstration of the additive effects of angiotensin-converting enzyme inhibition and angiotensin II antagonism in sodium depleted healthy subjects.

A blockade of the hemodynamic and tissue effects of angiotensin II (Ang II) more complete than that presently achieved with usual daily doses of angiotensin coverting enzyme (ACE) inhibitors or type 1 Ang II receptor antagonists has potential advantages and risks. Therefore, it is worthwhile to investigate the biological and the hemodynamic effects of the simultaneous blockade of the renin-angiotensin system (RAS) at the two sites where it can be currently achieved, ACE and type 1 Ang II receptors. To investigate this issue, 2 double-blind randomized crossover studies were performed in a model of mild sodium depletion in normotensive volunteers. They ingested single oral doses of captopril 50 mg, losartan 50 mg, their combination or matched placebos, and in a second study, single oral doses of enalapril 10 mg, enalapril 20 mg and the combination of losartan 50 mg with enalapril 10 mg. The combination of captopril 50 mg and losartan 50 mg had additive effects on blood pressure fall and renin release in sodium-depleted normotensive subjects. When compared to enalapril 10 mg and the doubling of its dose, the combination of losartan 50 mg and enalapril 10 mg significantly increased both the area under the time curve of mean blood pressure fall and plasma active renin levels. It did not further decrease plasma aldosterone levels. The conclusion is that a more complete blockade of the RAS can be achieved by concomitant administration of a type 1 Ang II receptor antagonist and an ACE inhibitor.

Aldosterone↗
PubMedDate not supplied

[Effect of furosemide and ACTH on plasma renin, aldosterone and cortisol levels in normal man].

Plasma renin activity (PRA), aldosterone and cortisol's variations are studied in normal salt repleted voluntary men (120 mEq/24 h sodium) before and after furosemide infusion and/or constant infusion of ACTH (beta 1-24 corticotrophin). PRA is determined by angiotensin I radioimmunoassay, plasma aldosterone by specific radioimmunoassay and plasma cortisol by competitive transcortine binding radioassay. 1) PRA and plasma aldosterone increase clearly after acute sodium depletion secundary to furosemide infusion; plasma cortisol increases a little. PRA and aldosterone's variations are identical after endogenous ACTH suppression by dexamethazone administration before study. 2) PRA is not influenced by constant infusion (16 ng/kg/mn) after acute infusion (0.3 mg intravenously) of ACTH (beta 1-24); plasma aldosterone and plasma cortisol increase dramatically and remain constant along the experience. 3) If acute sodium depletion is realized 120 mn after ACTH infusion, PRA still raises; on the other hand plasma aldosterone remains constant. These results confirm that acute sodium depletion stimulates aldosterone secretion by the way of renin angiotensin system then ACTH acts directly on the adrenal cortex. Nevertheless the stimulative action of acute sodium depletion on aldosterone secretion is suppressed by previous acute ACTH stimulation.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

[Numerical angiography in the evaluation of arterial hypertension].

Intravenous numeric angiography is a new method of medical imaging for investigation of possible renovascular causes of arterial hypertension. A non-invasive examination, it is less costly than conventional renal arteriography and can be performed in outpatients. Satisfactory images of the renal arteries were obtained in 80 p. cent of 200 hypertensive patients, and the presence of lesions was confirmed in 47 cases.

Adult↗
PubMedDate not supplied

Biochemical similarity of partially purified inactive renins from human plasma and kidney.

Inactive renin was partially purified from 4.5 liters of human plasma (502-fold, specific activity 0.8 X 10(-3) Goldblatt units/mg protein) and from 207 g renal cortex (103-fold, 52 X 10(-3) Goldblatt units/mg). In contrast to active renin, inactive renin from each source bound to Cibacron blue-agarose and was unable to bind to pepstatin-Sepharose. Both plasma and renal inactive renin had weaker affinity for anion-exchange resins than the active form, both bound to concanavalin A-Sepharose and were eluted with carbohydrate, and both bound tightly to hydrophobic gels. Each substance could be isolated in a completely inactive form during small-scale pilot studies, but "spontaneous" activation did occur, to a limited degree, during large-scale purification; this was possibly due to a plasma serine protease that fractionated with inactive renin during the initial purification steps. Both plasma and renal inactive renin were activated irreversibly by trypsin. Following activation, each substance lost it ability to bind to Cibacron blue-agarose. Each could be activated fully by acidification at 4 degrees C, but this activation was reversed during subsequent incubation at higher temperature and pH. There was no evidence of acid protease activity in either preparation. Activated inactive renin from both plasma and kidney were identical to partially-purified active renal renin in terms of pH optimum (pH 5.5-6.0) and reaction kinetics (Km 0.8-1.3 microM) with homologous angiotensinogen, noncompetitive inhibition by pepstatin (ki 2.5-3.5 microM), and an identical inhibition profile by monospecific antirenin antibodies. These results suggest that inactive renin from plasma and kidney may be the same substance and that their activated forms are similar to the endogenously produced active enzyme, consistent with the possibility that inactive renin is a precursor of circulating active renin.

Chromatography, Affinity↗