Diuretic therapy and response of essential hypertension to saralasin.

Thirty-four patients, most with a low-renin "essential" hypertension, and seven normal subjects were placed on diuretic therapy for 4 to 5 weeks. In the normal subjects, infusion of a highly specific, competitive angiotensin II analogue (1-sar-8-ala-angiotensin II, saralasin) did not significantly change recumbent blood pressure either before or after diuretic administration. In contrast, the hypertensive patients as a group had a low stimulated plasma renin activity before diuretic therapy and a rise in blood pressure during saralasin infusion. After therapy, the stimulated plasma renin activity was higher and saralasin produced a fall in blood pressure in some patients who were still hypertensive. The results suggest that short-term diuretic therapy, which is thought to act through its natriuretic effects, can convert some patients with essential hypertension, many with a low or a low-normal stimulated plasma renin activity, to individuals whose hypertension is supported by angiotensin II. The fall in blood pressure to saralsin infusion after diuretic therapy was directly proportional to the height to which diuretics elevated the stimulated plasma renin activity.