The effect of indomethacin on plasma renin activity and urinary aldosterone of patients with essential hypertension.

The effect of indomethacin on plasma renin activity (PRA), urinary aldosterone, 17 OH ketogenic steroids and plasma cortisol was studied in twenty-three patients with essential hypertension and compared in eleven patients to oxprenolol effect by 2 x 2 factorial trial. Indomethacin decreased PRA and urinary aldosterone: its effect was maintained when the drug was given for three days and it was related to basal PRA and aldosterone values. Therefore in patients with low PRA (renin-sodium index) PRA and aldosterone were unchanged, while they decreased in the normal high PRA group. Aldosterone changes were related to those of PRA, while 17 OH ketogenic steroids and plasma cortisol were unchanged. Both indomethacin and oxprenolol decreased PRA, but no interaction or additive effect was found between the two drugs. The present data indicate that indomethacin can decrease both PRA and aldosterone to an extent which is related to basal values and that aldosterone changes are mainly explained by those of PRA. The PRA unresponsiveness to indomethacin found in low renin patients may suggest renal prostaglandin deficiency. Finally the lack of interaction or of additive effect between indomethacin and oxprenolol may be explained by postulating either that the two drugs act on a common pathway or that an additive effect on PRA cannot be detected renin being maximally suppressed by full renal beta-receptors blockade.