Angiotensin converting enzyme inhibitors suppress the vascular renin-angiotensin system of spontaneously hypertensive rats.

The effects of angiotensin converting enzyme (ACE) inhibitors on the release of angiotensin II (Ang II) from isolated mesenteric arteries of spontaneously hypertensive rats (SHRs) were examined. Delapril, enalapril, and captopril suppressed Ang II release in a dose-dependent manner. After oral treatment with delapril (10 mg/kg/day), enalapril (10 mg/kg/day), and captopril (50 mg/kg/day) for 1 week, the blood pressure of SHRs was significantly reduced in the three groups and 54%, 46%, and 36% decreases in basal Ang II release were observed, respectively, compared with control. However, low-dose captopril (10 mg/kg/day) had no effect on blood pressure or basal Ang II release. These results provide clear evidence that ACE inhibitors suppress vascular renin-angiotensin activity of SHRs, and the possible contribution of the tissue renin-angiotensin system to spontaneous hypertension is suggested.