Coronary Vascular Actions of the Converting Enzyme Inhibitor, Enalapril

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Abstract
Enalapril, a potent angiotensin converting enzyme inhibitor, effectively blocked the constrictor actions of angiotensin I in isolated perfused cat coronary arteries. At concentrations of 25-100 .mu.g/ml, enalapril inhibited angiotensin I by 65-80%. Enalapril at 100-200 .mu.g/ml, markedly antagonized the coronary vasconstrictor effects of angiotensin II. At 150 .mu.g/ml, enlapril blocked the angiotensin II response by 80 .+-. 5% and at 200 .mu.g/ml, it was blocked by 95 .+-. 4%. Enalaprilic acid at 0.5-1.0 .mu.g/ml also blocked the angiotensin II response by 94 .+-. 5%. Captopril, up to 250 .mu.g/ml, failed to significantly antagonize angiotensin II, although it readily blocked angiotensin I in this preparation. The duration of this angiotensin II blockade lasted about 60-90 min. This angiotensin II antagonism may help explain the beneficial effects of enalapril in situations such as acute myocardial ischemia.