Altered renin-angiotensin-aldosterone relationships in normal renin essential hypertension.

Aldosterone responsiveness to angiotensin II (A II) was evaluated in 64 subjects with "normal renin" hypertension. Plasma aldosterone (PA) and plasma renin activity (PRA) levels were determined with the subjects supine and after 2 72 hours in the upright position while they were in metabolic balance on a 10 mEq of sodium/100 mEq of potassium diet. The increment in PA between supine and upright postures divided by the increment in PRA (APA/APRA) was used as an estimate of adrenal sensitivity to A II. Under identical conditions, the APA/APRA ratio in 11 normal controls was >3.8 . Although 52 of the hypertensive subjects had normal APA/APRA, 12 had low APA/APRA. Supine PA and PRA were similar in both groups, but the upright PA was lower (41 vs. 69 ng/dl) and the upright PRA higher (11.1 vs. 7 ng/ml per hr) in the group with the subnormal APA/APRA. The low APA/APRA ratios indirectly suggest subnormal aldosterone responsiveness to A II. To test this hypothesis directly, A II was infused into 19 of the 64 subjects (0 .1 ,0 .3 ,1 .0 , and 3.0 ng/kg per min). PA and A II levels were measured before and 20 and 30 min after each dose was begun. Blood pressure was monitored at 2-min intervals. In 14 hypertensives with normal APA/APRA, PA rose significantly during the 0.3,1.0, and 3.0 ng/kg per min doses. In five subjects with low APA/APRA, PA did not rise significantly at any dose of A II. Plasma A II levels and blood pressure rose comparably in both groups. These data demonstrate that, in the sodium-depleted state, some "normal renin" hypertensive subjects have decreased aldosterone but normal pressor responsiveness to angiotensin II.