The action of angiotensin on the isolated perfused cat heart

The effects of angiotensin I (AI) and angiotensin (AII) on myocardial contractility, heart rate and coronary perfusion were observed in the isolated perfused cat heart. AII (10^?11 mol) and AI (10^?10 mol) both caused slowly developing sustained increases in systolic pressure of approximately 55%. There were inconsistent small increases in heart rate. Coronary perfusion was initially diminished, but later increased to above control values during the positive inotropic effect. The actions of both AI and AII were blocked by 1 sar 8 ile AII (10^?9 mol). The converting enzyme inhibitors SQ 20881 (10^?8 mol) and SQ 14225 (10^?8 mol) blocked the effect of AI. The actions of AII or AI were not blocked by α or β adrenergic blockade or by prior treatment with reserpine.