apstatin and icatibant

Bradykinin is a potent endothelium-dependent vasodilator in the coronary vascular bed. Endothelial mediators released by bradykinin include nitric oxide, prostacyclin and as yet unidentified endothelium-derived hyperpolarising factors. We wished to determine the involvement of nitric oxide and prostaglandin pathways in the cardioprotective actions mediated by bradykinin via the combined inhibition of ACE and aminopeptidase P (APP) in an in vivo rat model of acute ischemia (30 min) and reperfusion (4h). Myocardial infarct size was measured by using the staining agent 2,3,5-triphenyl tetrazolium chloride (TTC). Lipid peroxide levels in serum and in heart tissue were estimated spectrophotometrically. A lead II electrocardiogram was monitored at various intervals throughout the experiment. Infarct size reduction obtained with the combined inhibition of enalapril and apstatin, lisinopril and apstatin was blocked partially but significantly with the prior administration of L-NAME (Nomega-nitro-L-arginine methyl ester) or aspirin, suggesting the involvement of both nitric oxide and prostaglandin pathways in the cardioprotective actions mediated by bradykinin.

Topics: Animals; Aspirin; Bradykinin; Disease Models, Animal; Drug Therapy, Combination; Enalapril; Female; Heart Rate; Injections, Intravenous; Lisinopril; Male; Malondialdehyde; Myocardial Infarction; Myocardial Reperfusion Injury; Myocardium; NG-Nitroarginine Methyl Ester; Peptides; Rats; Rats, Sprague-Dawley; Staining and Labeling; Tetrazolium Salts

Bradykinin is a potent vasoactive peptide that is known to elicit a number of biological responses. A number of peptidases have been identified to possess kininase activity, the inhibition of which increases the availability and effectiveness of kinins. We wished to determine the cardioprotective actions of an aminopeptidase P inhibitor, apstatin alone and in combination with enalapril/lisinopril/ramipril in an in vivo rat model of acute ischemia (30 min) and reperfusion (4 h). Myocardial infarction was produced by occlusion of the left anterior descending coronary artery for 30 min followed by 4 h of reperfusion. Infarct size was measured by using the staining agent 2,3,5-triphenyl tetrazolium chloride (TTC). Lipid peroxide levels in serum and in heart tissue were estimated spectrophotometrically. A lead II electrocardiogram was monitored at various intervals throughout the experiment. Infarct size was reduced to a greater extent with apstatin and with combined inhibition it was further reduced. Infarct size reduction obtained with the combined inhibition came to normal with the prior administration of B2 bradykinin antagonist HOE140 suggests the involvement of bradykinin in the cardioprotective actions of apstatin.

Topics: Angiotensin-Converting Enzyme Inhibitors; Animals; Bradykinin; Bradykinin Receptor Antagonists; Drug Therapy, Combination; Enalapril; Female; Heart Rate; Lipid Peroxides; Lisinopril; Male; Malondialdehyde; Myocardial Infarction; Myocardial Reperfusion Injury; Myocardium; Peptides; Ramipril; Rats; Rats, Sprague-Dawley; Time Factors

1. Inhibitors of the angiotensin converting enzyme (ACE) have been shown to exert their cardioprotective actions through a kinin-dependent mechanism. ACE is not the only kinin degrading enzyme in the rat heart. 2. Since aminopeptidase P (APP) has been shown to participate in myocardial kinin metabolism to the same extent as ACE, the aims of the present study were to investigate whether (a) inhibition of APP leads to a reduction of myocardial infarct size in a rat model of acute ischaemia and reperfusion, (b) reduction of infarct size is mediated by bradykinin, and (c) a combination of APP and ACE inhibition leads to a more pronounced effect than APP inhibition alone. 3. Pentobarbital-anaesthetized rats were subjected to 30 min left coronary artery occlusion followed by 3 h reperfusion. The APP inhibitor apstatin, the ACE-inhibitor ramiprilat, or their combination were administered 5 min before ischaemia. Rats receiving HOE140, a specific B(2) receptor antagonist, were pretreated 5 min prior to enzyme inhibitors. Myocardial infarct size (IS) was determined by tetrazolium staining and expressed as percentage of the area at risk (AAR). 4. IS/AAR% was significantly reduced in rats that received apstatin (18+/-2%), ramiprilat (18+/-3%), or apstatin plus ramiprilat (20+/-4%) as compared with those receiving saline (40+/-2%), HOE (43+/-3%) or apstatin plus HOE140 (49+/-4%). 5. Apstatin reduces IS in an in vivo model of acute myocardial ischaemia and reperfusion to the same extent than ramiprilat. Cardioprotection achieved by this selective inhibitor of APP is mediated by bradykinin. Combined inhibition of APP and ACE did not result in a more pronounced reduction of IS than APP-inhibition alone.

Topics: Aminopeptidases; Angiotensin-Converting Enzyme Inhibitors; Animals; Blood Pressure; Bradykinin; Bradykinin Receptor Antagonists; Heart; Heart Rate; Hemodynamics; Kinins; Male; Myocardial Infarction; Myocardium; Peptides; Protease Inhibitors; Ramipril; Rats; Rats, Wistar; Receptor, Bradykinin B2

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