Effect of ACE inhibition on pressor, renal vascular, and adrenal responsesto infusion of angiotensin I in normal subjects eating a low-salt diet

To examine the influence of angiotensin-converting enzyme (ACE) on presser, renal vascular, and adrenal responses during angiotensin I (Ang I) infusio n, we studied 10 normotensive, healthy men. Each was in balance with a 10-m Eq sodium, 100-mEq potassium intake and was studied before and during ACE i nhibition with enalapril. Ang I (3, 10, and 30 ng/kg/min) was infused in ea ch subject. Then ACE inhibition was instituted with enalapril for 3 days, w hich induced the anticipated fall in blood pressure, plasma Ang II, and ald osterone concentration, and rise in renal plasma flow. During ACE inhibitio n only the 30-ng/kg/min Ang I dose raised plasma Ang II levels. There was a spectrum, however, in the end-organ response to Ang I during ACE inhibitio n. Responses of plasma aldosterone concentration and blood pressure were in excellent accord with the reduction in Ang II formation. On the other hand , responses of the renal blood supply were substantially less inhibited tha n anticipated. Under the conditions of this study, ACE inhibition led to no nuniform changes in the response to exogenous Ang I, suggesting intrarenal conversion of Ang I to Ang II. (C) 2000 American Journal of Hypertension, L td.