BRADYKININ PATHWAY IS INVOLVED IN ACUTE HEMODYNAMIC-EFFECTS OF ENALAPRILAT IN DOGS WITH HEART-FAILURE

To determine the role of the renin-angiotensin system and the bradykin in pathway in the mechanism of action of angiotensin-converting enzyme inhibitors in heart failure, the acute effects of enalaprilat (1 mg/k g) were compared with those of a renin inhibitor (ciprokiren, 1 mg/kg iv) in 10 chronically instrumented conscious dogs with heart failure i nduced by right ventricular pacing (3 wk, 240 beats/min). The effects of enalaprilat and ciprokiren on bradykinin infusion (3, 10, and 30 mu g/min) and the effects of enalaprilat in the presence of the bradykin in Bz receptor antagonist Hoe-140 (10 mu g/kg iv) were also examined. Both inhibitors significantly decreased mean aortic pressure and incre ased cardiac output. However, enalaprilat induced significantly greate r hemodynamic effects than ciprokiren (mean aortic pressure, -13 +/- 3 vs. -6 +/- 1 mmHg; cardiac output, 0.4 +/- 0.1 vs. 0.15 +/- 0.1 l/min ). Bradykinin infusion led to dose-dependent decreases in mean aortic pressure and increases in cardiac output that were not modified by pre treatment with ciprokiren but were potentiated 10-fold by enalaprilat. Hoe-140 significantly reduced the hemodynamic effects of enalaprilat. Thus endogenous bradykinin is involved in the acute hemodynamic effec ts of enalaprilat in experimental heart failure.