Triamterene-induced changes in aldosterone and renin values in essential hypertension. Evidence of a role for aldosterone in preventing blood pressure reduction.

The effect of triamterene, a potassium-retaining natriuretic and diuretic agent, on arterial blood pressure was studied in 31 patients with essential hypertension; there were seven patients with low plasma renin activity and 24 patients with normal plasma renin activity. Triamterene exhibited mild antihypertensive action, somewhat more pronounced in the low-renin group. The patients were also analyzed by considering them in terms of their blood pressure response. Of the 21 patients in the nonresponder group, no blood pressure decrease occurred, despite induced volume depletion accompanied by an increased plasma renin activity and a concomitant rise in the aldosterone excretion. In contrast, the ten patients in the responder group exhibited a fall in blood pressure, but the aldosterone excretion rate did not change significantly, even though plasma renin activity increased significantly. Moreover, only in the nonresponder group did the stimulated aldosterone excretion rate correlate significantly with the stimulated plasma renin activity. Thus, the failure of triamterene to lower blood pressure in the nonresponder group can be closely related to a significant increase in aldosterone excretion rate. The data suggest the operation of a reactive pressor action mediated by aldosterone, independent of its sodium-retaining effect.