Angiotensin-converting enzyme inhibitor (SQ 20881) in the diagnosis of renovascular hypertension.

SQ 20881, an angiotensin-converting enzyme inhibitor, was given to 12 patients with renovascular hypertension and to 1 patient with unilateral parenchymatous renal disease in order to evaluate the role of renin-angiotensin systems in their hypertension. Plasma renin activity (PRA) and aldosterone were assayed in systemic blood before and after the injection of SQ 20881. In 5 patients PRA was also measured separately in each renal vein. Blood pressure decreased, PRA increased, and aldosterone level decreased in the 12 renin-dependent patients. When PRA was sampled separately from each renal vein, the increase was larger on the side of the affected kidney. Four patients with a positive test underwent corrective surgery, and in all blood pressure became normal. SQ 20881 is a useful agent in evaluating the contribution of renin in patients with hypertension.