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

Abstract

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 1/2 h in the upright position while they were in metabolic balance on a 10 meq of Na/100 meq of K diet. The increment in PA between supine and upright postures divided by the increment in PRA (.DELTA.PA/.DELTA.PRA) was used as an estimate of adrenal sensitivity to A II. Under identical conditions, .DELTA.PA/.DELTA.PRA ratio in 11 normal controls was > 3.8. Although 52 of the hypertensive subjects had normal .DELTA.PA/.DELTA.PRA, 12 had low .DELTA.PA/.DELTA.PRA. Supine PA and PRA were similar in both groups, but upright PA was lower (41 vs. 69 ng/dl) and upright PRA higher (11.1 vs. 7 ng/ml per h) in the group with the subnormal .DELTA.PA/.DELTA.PRA. Low .DELTA.PA/.DELTA.PRA 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 began. Blood pressure was monitored at 2 min intervals. In 14 hypertensives with normal .DELTA.PA/.DELTA.PRA, PA rose significantly during the 0.3, 1.0 and 3.0 ng/kg per min doses. In 5 subjects with low .DELTA.PA/.DELTA.PRA, PA did not rise significantly at any dose of A II. Plasma A II levels and blood pressure rose comparably in both groups. In the Na-depleted state, some normal renin hypertensive subjects have apparently decreased aldosterone but normal pressor responsiveness to angiotensin II.