cyclic-gmp and ramiprilat

The antihypertrophic action of angiotensin (Ang)-converting enzyme (ACE) inhibitors in the heart is attributed in part to potentiation of bradykinin. Bradykinin prevents hypertrophy of cultured cardiomyocytes by releasing nitric oxide (NO) from endothelial cells, which increases cardiomyocyte guanosine 3'5'-cyclic monophosphate (cyclic GMP). It is unknown whether cyclic GMP is essential for the action of bradykinin, or whether findings in isolated cardiomyocytes apply in whole hearts, in the presence of other cell types and mechanical/dynamic activity. We now examine the contribution of cyclic GMP to the antihypertrophic action of bradykinin in cardiomyocytes and perfused hearts. In adult rat isolated cardiomyocytes cocultured with bovine aortic endothelial cells, the inhibitory action of bradykinin (10 micromol/L) against Ang II (1 micromol/L)-induced [3H]phenylalanine incorporation was abolished by the soluble guanylyl cyclase inhibitor [1,2,4] oxadiazolo[4,3-a]quinoxalin-1-one (10 micromol/L). In Langendorff-perfused rat hearts, Ang II (10 nmol/L)-induced increases in [3H]phenylalanine incorporation and atrial natriuretic peptide mRNA expression were prevented by bradykinin (100 nmol/L), the NO donor sodium nitroprusside (3 micromol/L), and the ACE inhibitor ramiprilat (100 nmol/L). The acute antihypertrophic action of bradykinin was accompanied by increased left ventricular cyclic GMP, and the ramiprilat effect was attenuated by HOE 140 (1 micromol/L, a B2-kinin receptor antagonist) or [1,2,4] oxadiazolo[4,3-a]quinoxalin-1-one (100 nmol/L). In conclusion, bradykinin exerts a direct inhibitory action against the acute hypertrophic response to Ang II in rat isolated hearts, and elevation of cardiomyocyte cyclic GMP may be an important antihypertrophic mechanism used by bradykinin and ramiprilat in the heart.

Topics: Angiotensin-Converting Enzyme Inhibitors; Animals; Bradykinin; Cardiomegaly; Cattle; Cells, Cultured; Coronary Circulation; Cyclic GMP; Heart; Heart Rate; Male; Myocardium; Nitric Oxide Donors; Organ Culture Techniques; Phenylalanine; Ramipril; Rats; Rats, Sprague-Dawley

In heart failure atrial natriuretic peptide (ANP) release in response to volume expansion is impaired while the renin-angiotensin system is activated. This study was designed to test the hypothesis that ANP release in heart failure is dependent on an activated angiotensin system.. We studied the ANP and renin-angiotensin systems in a rat model of shunt-induced high-output heart failure, in which we rapidly increased circulating fluid volume with a 5 ml, hyperoncotic infusion, and evaluated the effects of acute inhibition of the angiotensin converting enzyme as well as of the blockade of the angiotensin II type 1 receptors on the ANP release and on renal excretory function.. ANP and angiotensin II plasma concentrations prior to volume expansion were elevated (p < 0.05) in rats with aortocaval shunt compared to controls. The diuretic response to acute volume expansion (18.5 +/- 1.5 vs. 48.2 +/- 2.4 microliters/min, p < 0.001) was markedly blunted. ANP release was attenuated in rats with aortocaval shunt, as was the increase of its second messenger cGMP in plasma and urine. The blunted increase in ANP plasma levels was not due to depleted cardiac stores as cardiac ANP content, as well as ANP synthesis, were increased (p < 0.05). Acute inhibition of the angiotensin converting enzyme as well as blockade of the angiotensin II type 1 receptors restored ANP release in response to volume expansion (p < 0.01). Moreover, acute inhibition of the renin-angiotensin system completely normalized the diuretic response.. Our data suggest that the ANP system is impaired in rats with aortocaval shunt. The activation of the angiotensin system contributes to the impairment of the ANP system. Acute inhibition of the angiotensin II system significantly improved the ability of the ANP system to respond to acute volume expansion. Our findings indicate a hitherto fore unappreciated interaction between both systems and suggest additional mechanisms for the beneficial effects of angiotensin converting enzyme inhibition or angiotensin II type 1 receptor antagonists in heart failure.

Topics: Angiotensin II; Angiotensin Receptor Antagonists; Angiotensin-Converting Enzyme Inhibitors; Animals; Atrial Natriuretic Factor; Blood Volume; Cyclic GMP; Diuresis; Heart Failure; Male; Myocardium; Ramipril; Rats; Rats, Wistar; Renin-Angiotensin System; Statistics, Nonparametric; Tetrazoles; Valine; Valsartan

We studied whether primary cultured porcine brain capillary endothelial cells (PBCEC) respond to bradykinin with an enhanced intracellular cytosolic calcium concentration [Ca2+]i with subsequent formation of nitric oxide (NO) and prostacyclin (PGI2). In addition we examined whether these cells synthetize and release kinins that may accumulate during angiotensin-converting enzyme (ACE) inhibition. [Ca2+]i was assessed by the fluorescent dye Fura-2, NO formation by determination of intracellular cyclic GMP and PGI2 by a specific radioimmunoassay for 6-ketoprostaglandin F1 alpha. Bradykinin and the ACE inhibitor ramiprilat concentration-dependently increased the formation of cyclic GMP which was completely prevented by the stereospecific inhibitor of NO synthase, NG-nitro-L-arginine. Also the specific B2-kinin receptor antagonist icatibant (Hoe 140) abolished the increase in cyclic GMP as well as the ramiprilat-induced increase in PGI2 formation. The data demonstrate the existence of B2-kinin receptors and ACE activity in PBCEC. Moreover PBCEC are capable of producing and releasing kinins in amounts that lead via stimulation of B2-kinin receptors to an enhanced [Ca2+]i as well as NO and PGI2 synthesis and release, provided that degradation of kinins is prevented by inhibition of endothelial ACE activity.

Topics: 1-Methyl-3-isobutylxanthine; 6-Ketoprostaglandin F1 alpha; Angiotensin-Converting Enzyme Inhibitors; Animals; Arginine; Bradykinin; Calcium; Capillaries; Cells, Cultured; Cerebrovascular Circulation; Cyclic GMP; Cytosol; Dose-Response Relationship, Drug; Endothelium, Vascular; Epoprostenol; Fura-2; Kinetics; Nitric Oxide; Nitroarginine; Ramipril; Swine

The effects of angiotensin-converting enzyme (ACE) inhibitors on endothelial autacoid formation were determined in human cultured endothelial cells and in endothelium-intact bovine coronary arteries under resting conditions and after stimulation with bradykinin. Incubation of cultured human endothelial cells with moexiprilat or ramiprilat (0.3 microM) caused a maintained increase in resting intracellular calcium [Ca2+]i, which was prevented by the selective B2-receptor antagonist Hoe 140 (0.1 microM). Both ACE inhibitors also significantly enhanced the increase in [Ca2+]i elicited by bradykinin (3 nM). In parallel with their effect on resting [Ca2+]i, moexiprilat and ramiprilat both induced an increase in intracellular cyclic GMP (cGMP). This increase was prevented by Hoe 140 (0.1 microM) and was abolished by NG-nitro-L-arginine (30 microM), indicating a kinin-induced nitric oxide (NO) formation in this response. The elevation in [Ca2+]i also led to an enhanced production of prostacyclin (PGI2), as indicated by an increase in the concentration of 6-keto prostaglandin F1 alpha (PGF1 alpha) in the cell supernatant. Similar effects of the ACE inhibitors on endothelial autacoid production were observed in endothelium-intact bovine coronary arteries. Like bradykinin (30 nM), moexiprilat (0.3 microM) elicited a nearly twofold increase in the cGMP content of these arteries, which was abolished by both NG-nitro-L-arginine and removal of the endothelium. The functional consequences of this ACE inhibitor-induced increase in vascular cGMP were reflected by a distinct relaxation of arteries preconstricted with PGF2 alpha.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 6-Ketoprostaglandin F1 alpha; Angiotensin-Converting Enzyme Inhibitors; Animals; Arginine; Bradykinin; Calcium; Cattle; Cells, Cultured; Coronary Vessels; Cyclic GMP; Endothelium, Vascular; Epoprostenol; Humans; Isoquinolines; Nitric Oxide; Nitroarginine; Ramipril; Tetrahydroisoquinolines; Umbilical Veins; Vasodilation

The angiotensin converting enzyme (ACE) inhibitors, moexiprilat and ramiprilat, relaxed preconstricted endothelium-intact bovine coronary artery rings and enhanced the relaxant response to bradykinin. The relaxation was observed in the presence of a cyclooxygenase inhibitor and without previous exposure to bradykinin. ACE inhibitor-dependent relaxation was attenuated by the selective B2-kinin receptor antagonist, Hoe 140, and completely abolished by removal of the endothelium. Bradykinin or moexiprilat also significantly increased the cyclic guanosine monophosphate (cGMP) content of these coronary segments, an effect which was abolished by the nitric oxide (NO) synthase inhibitor, NG-nitro-L-arginine (NNA), or by removal of the endothelium. NNA also diminished the relaxant response to moexiprilat, but only partially inhibited that to bradykinin, suggesting that the ACE inhibitor-induced relaxation was predominantly mediated by endothelial NO release, whereas bradykinin acted in part by another endothelium-dependent mechanism. These findings indicate that ACE inhibitors can elicit endothelium-dependent relaxations presumably by facilitating the accumulation of endothelium-derived kinins in or at the vessel wall. This local mechanism may significantly contribute to the antihypertensive action of these compounds in vivo.

Topics: Angiotensin-Converting Enzyme Inhibitors; Animals; Arginine; Bradykinin; Cattle; Coronary Vessels; Cyclic GMP; Endothelium, Vascular; In Vitro Techniques; Isoquinolines; Nitric Oxide; Nitroarginine; Ramipril; Tetrahydroisoquinolines; Vasodilation

We have investigated in human endothelial cells in culture the effects of angiotensin-converting enzyme (ACE) inhibitors on the concentration of intracellular free Ca2+ ([Ca2+]i) and the formation of nitric oxide (NO) and prostacyclin (PGI2). Enalaprilat, moexiprilat and ramiprilat similarly potentiated the increase in [Ca2+]i elicited by bradykinin and caused an increase in resting [Ca2+]i when given alone. The latter effect was long-lasting and accompanied by an increased formation of NO and PGI2. All of these effects were inhibited by the B2-kinin receptor antagonist Hoe 140, suggesting that the endogenous synthesis/release of bradykinin represents an autocrine mechanism for the stimulation of endothelial autacoid formation. Thus these findings strongly support the concept that ACE inhibitors promote local vasodilation by increasing the level of bradykinin generated in subthreshold concentrations by the endothelium.

Topics: 1-Methyl-3-isobutylxanthine; Angiotensin-Converting Enzyme Inhibitors; Bradykinin; Calcium; Cells, Cultured; Cyclic GMP; Enalaprilat; Endothelium, Vascular; Epoprostenol; Humans; Isoquinolines; Kinetics; Peptidyl-Dipeptidase A; Ramipril; Tetrahydroisoquinolines; Umbilical Veins

We have investigated the effects of angiotensin-converting enzyme (ACE) inhibitors on intracellular Ca2+ levels in human cultured endothelial cells and on endothelial autacoid formation in endothelium-intact bovine coronary arteries and in isolated perfused rabbit and rat hearts. Incubation of cultured endothelial cells with ramiprilat (0.3 microM) caused a maintained increase in resting intracellular Ca2+. This effect was long-lasting, accompanied by an increased formation of both nitric oxide (NO) and prostacyclin (PGI2), and was abolished by the specific B2-kinin receptor antagonist Hoe 140. Ramiprilat also significantly enhanced the increase in intracellular Ca2+ elicited by bradykinin (3 nM). In endothelium-intact bovine coronary arteries, moexiprilat (0.3 microM), like bradykinin (30 nM), caused a nearly twofold increase in the vascular cGMP content which was abolished by both NG-nitro-L-arginine (30 microM) and removal of the endothelium. The functional consequences of this ACE inhibitor-induced increase in vascular cGMP content were reflected by a distinct relaxation of the coronary segments preconstricted with prostaglandin F2 alpha. In the isolated perfused rabbit heart, ramiprilat (0.3 microM) affected neither resting vascular tone nor endothelial autacoid release; however, the vasodilation and release of PGI2 in response to exogenously applied bradykinin (10 nM) were significantly enhanced by ramiprilat. This effect was also seen using moexiprilat (0.1 microM) in the isolated perfused rat heart. Although these findings suggest that endothelium-derived bradykinin is not involved in the control of resting vascular tone in the coronary microcirculation of the rabbit and the rat, there appears to be significant ACE activity to modulate bradykinin-induced endothelial autacoid formation.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Angiotensin-Converting Enzyme Inhibitors; Animals; Bradykinin; Calcium; Cells, Cultured; Coronary Vessels; Cyclic GMP; Endothelium, Vascular; Epoprostenol; Female; Humans; Isoquinolines; Male; Muscle Relaxation; Muscle, Smooth, Vascular; Nitric Oxide; Rabbits; Ramipril; Rats; Rats, Wistar; Tetrahydroisoquinolines; Vasodilation

The role of NO-formation induced by accumulated endogenous bradykinin (BK) via local ACE-inhibition with ramiprilat (RT) or by adding BK exogenously was evaluated in cultured bovine aortic endothelial cells (BAEC) and in isolated rat hearts with post-ischaemic reperfusion injuries. Furthermore we used the n-octyl-ester of ramipril (RA-octil) which was shown to have no ACE-inhibitory action. In BAEC, ACE-inhibition by RT (1 x 10(-8)-1 x 10(-6) mol/l) or addition of BK (1 x 10(-8)-1 x 10(-6) mol/l) stimulated the formation of NO and prostacyclin (PGI2) as assessed by endothelial cyclic GMP- and 6-keto-PGF1a formation. Cyclic GMP and PGI2 synthesis was completely suppressed by the NO synthase inhibitor NG-nitro-L-arginine (L-NNA, 1 x 10(-5) mol/l) and by the B2 kinin receptor antagonist HOE 140 (1 x 10(-7) mol/l). RA-octil (1 x 10(-8)-1 x 10(-4) mol/l) did not affect endothelial cyclic GMP production in BAEC. In isolated working rat hearts subjected to local ischemia with reperfusion both RT (1 x 10(-8) mol/l) and BK (1 x 10(-9) mol/l) reduced the incidence and duration of ventricular fibrillation. In parallel myocardial function (left ventricular pressure, coronary flow) and metabolism (high energy rich phosphates) were improved showing a comparable fingerprint for RT and BK. Addition of L-NNA (1 x 10(-6) mol/l) or HOE 140 (1 x 10(-9) mol/l) abolished these protective effects of RT and BK. As in the BAEC studies RA-octil was without beneficial effects on the isolated ischaemic rat heart. The findings on BAEC show that inhibition of ACE localized on the luminal side of the vascular endothelium results in increased synthesis of NO and prostacyclin by local accumulation of endothelium-derived BK. Similar mechanisms may occur in the ischaemic rat heart leading to cardioprotection.

Topics: Angiotensin-Converting Enzyme Inhibitors; Animals; Arrhythmias, Cardiac; Bradykinin; Cattle; Cells, Cultured; Cyclic GMP; Endothelium, Vascular; Epoprostenol; Female; In Vitro Techniques; Male; Myocardial Ischemia; Myocardial Reperfusion Injury; Nitric Oxide; Ramipril; Rats; Rats, Wistar

Like bradykinin the converting enzyme inhibitor ramiprilat concentration-dependently enhances the formation of nitric oxide and prostacyclin assessed by intracellular cyclic GMP accumulation and 6-keto prostaglandin F1. resp. Both ramiprilat-induced effects are completely suppressed by the specific kinin receptor antagonist Hoe 140. The ramiprilat-induced cyclic GMP increase is totally blocked by the stereospecific inhibitor of nitric oxide synthase, NG-nitro-L-arginine.

Topics: Angiotensin-Converting Enzyme Inhibitors; Animals; Aorta; Arginine; Bradykinin; Captopril; Cattle; Cells, Cultured; Cyclic GMP; Endothelium, Vascular; Epoprostenol; Nitric Oxide; Nitroarginine; Ramipril

We studied whether inhibition of angiotensin converting enzyme stimulates the formation of nitric oxide and prostacyclin in cultured human and bovine endothelial cells by an enhanced accumulation of endothelium-derived bradykinin. Nitric oxide formation was assessed in terms of intracellular cyclic GMP accumulation, prostacyclin release by a specific radioimmunoassay. Inhibition of angiotensin converting enzyme by ramiprilat dose- and time-dependently increased the formation of nitric oxide and prostacyclin. These increases, peaking within 10 minutes, were maintained for at least 60 minutes. The ramiprilat-induced cyclic GMP increase was completely abolished by the stereospecific inhibitor of nitric oxide synthase, NG-nitro-L-arginine. The B2-kinin receptor antagonist, Hoe 140 (0.1 microM), markedly attenuated the cyclic GMP accumulation and abolished the increase in prostacyclin release. The supernatant of endothelial cells, incubated with ramiprilat (0.3 microM) for 15 minutes, elicited a significant nitric oxide release (as assessed by a guanylyl cyclase assay) in untreated endothelial cells used as detector tissue. Preincubation of the detector cells with Hoe 140 completely abolished this nitric oxide release. These data indicate that cultured endothelial cells from different species are capable of producing and releasing bradykinin into the extracellular space in amounts that lead to a sustained stimulation of nitric oxide and prostacyclin formation, provided that bradykinin degradation is prevented by angiotensin converting enzyme inhibition. Thus, the protective effect of angiotensin converting enzyme inhibitors observed on endothelial vasomotor function in hypertension may be explained by the local accumulation of endothelium-derived bradykinin that acts in an autocrine and paracrine manner as potent stimulus for endothelial autacoid formation.

Topics: Angiotensin-Converting Enzyme Inhibitors; Bradykinin; Cells, Cultured; Cyclic GMP; Endothelium, Vascular; Epoprostenol; Humans; Nitric Oxide; Pyrroles; Ramipril