cardiovascular-agents and ramiprilat

1. Pretreatment with ramiprilat, an angiotensin-converting enzyme (ACE) inhibitor, induced cardioprotection and its possible mechanism of action was investigated in guinea-pig Langendorff perfused heart. 2. Superoxide anion (*O2-), produced by hypoxanthine and xanthine oxidase, and the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical were used for triggering free radical injury in cardiac tissue. 3. 1,1-Diphenyl-2-picryl-hydrazyl and *O2- significantly reduced left ventricular developed pressure (LVDP), +/-dP/dt(max), heart rate and coronary flow. Left ventricular end-diastolic pressure (LVEDP) was elevated and lactate dehydrogenase (LDH) leakage and the formation of thiobarbituric acid-reactive substances (TBARS) formation were significantly increased. 4. Pretreatment with ramiprilat induced cardioprotection against DPPH and *O2- free radical injury. Cardiac functions (LVDP, LVEDP and +/-dP/dt(max)) were significantly improved. Both LDH and TBARS were reduced. 5. HOE 140 (a selective bradykinin B2 receptor antagonist), calphostin C (a protein kinase C (PKC) inhibitor) and indomethacin (a cyclo-oxygenase inhibitor) all abolished the cardiac protective effect of ramiprilat. However, N(G)-nitro-L-arginine methyl ester, a nitric oxide synthase inhibitor, had no effect. 6. In conclusion, ramiprilat pretreatment induces cardioprotection against either DPPH or *O2- free radical injury. The protective effect depends on activation of B2 receptors and PKC. Prostaglandin synthesis is also involved.

Topics: Angiotensin-Converting Enzyme Inhibitors; Animals; Bepridil; Biphenyl Compounds; Bradykinin; Bradykinin Receptor Antagonists; Cardiovascular Agents; Cyclooxygenase Inhibitors; Diastole; Free Radicals; Guinea Pigs; Heart; Heart Rate; In Vitro Techniques; Indomethacin; L-Lactate Dehydrogenase; Male; Myocardium; Naphthalenes; NG-Nitroarginine Methyl Ester; Picrates; Prostaglandins; Protein Kinase C; Ramipril; Receptors, Bradykinin; Thiobarbituric Acid Reactive Substances; Ventricular Function, Left

Because part of the cardioprotective effects of angiotensin-converting enzyme (ACE) inhibitors results from their protective effects on cardiac bradykinin (BK) metabolism, the purpose of this study was to define the metabolism of BK in normal and failing human hearts and to compare the effect of omapatrilat, a vasopeptidase inhibitor (VPI), which simultaneously inhibits both neutral endopeptidase (NEP) and ACE, with that of an ACE inhibitor. Exogenous BK at a nanomolar concentration was incubated alone, in the presence of an ACE inhibitor (ramiprilat, 36 nM), or in the presence of a VPI (omapatrilat, 61 nM) with left ventricular membranes prepared from normal donor hearts (n = 7), and hearts from patients with an ischemic (n = 11) or dilated (n = 12) cardiomyopathy (DCM). The half-lives calculated for BK alone (199 +/- 60, 224 +/- 108, and 283 +/- 122 s; P = NS) exhibited similar values for normal, ischemic, and DCM heart tissues, respectively. Ramiprilat significantly increased the half-life of BK (P <.01), but the effect was similar for the three kinds of tissues (297 +/- 104, 267 +/- 157, and 407 +/- 146 s, respectively; P = NS). The potentiating effect of the VPI omapatrilat on the kinetic parameter of BK (478 +/- 210, 544 +/- 249, and 811 +/- 349 s, respectively) was greater than that of the ACE inhibitor (P <.01). Moreover, omapatrilat had a more important potentiating effect with DCM than normal heart membranes (P <.05). These results show that not only ACE but also and mainly NEP play an important role in the degradation of BK in human heart membranes. Omapatrilat, a VPI, has a greater protective effect on BK metabolism than that of a pure ACE inhibitor. Thus, inhibition of both ACE and NEP with omapatrilat could be more cardioprotective than ACE inhibition alone.

Topics: Angiotensin-Converting Enzyme Inhibitors; Bradykinin; Cardiomyopathy, Dilated; Cardiovascular Agents; Female; Half-Life; Heart; Humans; Male; Membranes; Middle Aged; Myocardial Ischemia; Myocardium; Neprilysin; Peptidyl-Dipeptidase A; Protease Inhibitors; Pyridines; Ramipril; Thiazepines

Aminopeptidase P and angiotensin-converting enzyme (ACE) are responsible for the metabolism of exogenously administered bradykinin in the coronary circulation of the rat. It has been shown that ACE inhibitors decrease cytosolic enzyme release from the ischemic rat heart and reduce reperfusion-induced ventricular arrhythmias by increasing endogenous levels of bradykinin. It was hypothesized that the aminopeptidase P inhibitor apstatin could do the same. In an isolated perfused rat heart preparation subjected to global ischemia and reperfusion, both apstatin and ramiprilat (an ACE inhibitor) significantly decreased creatine kinase (CK) and lactate dehydrogenase (LDH) release. The difference between the postischemia and preischemia levels of released CK was reduced 68% by apstatin and 68% by ramiprilat compared with control. The corresponding reductions in LDH release were 74% for apstatin and 81% for ramiprilat. A combination of the inhibitors was not significantly better than either one alone. Apstatin and ramiprilat also significantly reduced the duration of reperfusion-induced ventricular fibrillation by 69 and 61%, respectively. The antiarrhythmic effect of apstatin was reversed by HOE140, a bradykinin B2-receptor antagonist, suggesting that apstatin is acting by potentiating endogenously formed bradykinin. The results demonstrate that the aminopeptidase P inhibitor apstatin is cardioprotective in this model of cardiac ischemia/ reperfusion injury.

Topics: Adrenergic beta-Antagonists; Angiotensin-Converting Enzyme Inhibitors; Animals; Arrhythmias, Cardiac; Bradykinin; Cardiovascular Agents; Creatine Kinase; Drug Interactions; In Vitro Techniques; L-Lactate Dehydrogenase; Male; Peptides; Perfusion; Protease Inhibitors; Ramipril; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Ventricular Fibrillation