The effect of renin and aldosterone inhibition by β-adrenergic blockade on the response to the new diuretic azosemide

Abstract

The effect of repeated Azosemide infusions (20 mg in 500 ml 5% glucose for one h) on urine volume and electrolyte excretion, and on the activity of the renin-angiotensin-aldosterone system (RAAS) was studied in a group of 15 patients with benign essential hypertension before and during treatment with the β-adrenergic blocker Trimepranol. Azosemide alone had a marked but short-lasting diuretic and natriuretic effect. Repeated administration on three consecutive days led, however, to a progressive decrease in the natriuretic effectiveness of Azosemide, associated with an increase in plasma renin activity (from 0.413 ± 0.123 to 2.631 ± 0.421 pmol/1/sec and in plasma aldosterone concentration (from 0.335 ± 0.032 to 1.687 ± 0.438 pmol/l). Treatment with Trimepranol 30 mg/day enhanced and prolonged the diuretic and natriuretic response to Azosemide concomitantly with a reduction of its stimulatory effect on RAAS. These results suggest that stimulation of the RAAS might be responsible for the diminishing effectiveness of repeated Azosemide infusions and that the stimulation could be, at least partly, inhibited by a β-blocker Trimepranol, resulting in a greater diuretic and natriuretic effect of Azosemide.