Effects of chronic heart failure on the responsiveness to angiotensin I and to angiotensin converting enzyme inhibition with cilazapril in rats.

1. The effects of heart failure due to chronic myocardial infarction on the responsiveness to injected angiotensin I and ACE inhibition by intravenous cilazapril (1 mg kg-1) were evaluated. 2. For this purpose one group of 17 rats with a 4-week old myocardial infarction was compared with a group of 10 sham operated rats. 3. Heart failure increased markedly the responsiveness of the renal and mesenteric vascular beds to ACE inhibition which produced a vasodilation in these two vascular beds. 4. This increased responsiveness was most likely due to a stimulation of the renin-angiotensin system without any change of sensitivity to angiotensin I of the renal and mesenteric vascular beds. 5. Cilazapril produced the same level of ACE inhibition in both groups of rats.