Converting Enzyme Inhibition during Chronic Angiotensin II Infusion in Rats: Evidence against a Non-Angiotensin Mechanism

1. To investigate the non-angiotensin effects of converting enzyme inhibition, angiotensin II was infused intravenously at 30 ng/min for 9 days in conscious rats to produce moderate blood pressure elevation. One group was given captopril (SQ 14 225) by gavage (100 mg/kg twice daily) and the other glucose. 2. After 7 days of captopril administration, enzyme blockade was confirmed by a tenfold greater depressor sensitivity to exogenous bradykinin and a markedly decreased plasma angiotensin converting enzyme activity. 3. Mean arterial pressure, heart rate and plasma renin activity were not different between captopril and glucose-treated groups in the presence of angiotensin II. Metabolic studies also revealed no long-term differences in water and food intake, weight change or sodium and potassium metabolism. 4. These findings suggest that, in the presence of angiotensin II, there is no detectable haemodynamic or metabolic effect of converting enzyme inhibition in rats and, therefore, that bradykinin plays little or no role in its long-term antihypertensive action.