EFFECTS OF ANGIOTENSIN-CONVERTING ENZYME-INHIBITION ON RENAL SODIUM HANDLING AFTER FUROSEMIDE INJECTION

The goal of this study was to quantitate the effect of angiotensin-con verting enzyme inhibition on renal sodium handling after furosemide in jection. The study was carried out on low and normal salt intake to as sess potential interaction with salt balance. Eighteen healthy normote nsive volunteers were examined in a double placebo-controlled parallel group design. Subjects were randomly put on either low-salt (20 mmol/ day) or normal-salt (110 mmol/day) diet. In either arm of the diet vol unteers were first treated orally with placebo for 1 week and subseque ntly with 2.5 mg/day of the angiotensin-converting enzyme inhibitor ci lazapril for another 1 week. Cumulative 24-h urinary sodium excretion was measured on the 6th day of the respective week after sham injectio n and on the 7th day after injection of 40 mg furosemide. Compared to pretreatment with placebo, pretreatment with cilazapril resulted in a higher cumulative sodium excretion after furosemide injection (day 7) than after the sham injection (day 6) on both salt intakes. The differ ence in natriuresis (cilazapril versus placebo) was evident 2 and 3 h after injection of furosemide. Neither the time of onset nor the magni tude of antinatriuresis were affected by cilazapril. Following furosem ide angiotensin II increased significantly even after cilazapril pretr eatment. Cilazapril tended to reduce urinary furosemide excretion. At any given urinary furosemide concentration, the increment in urinary s odium excretion was significantly greater with cilazapril irrespective of salt intake. The study shows that (a) cilazapril increases furosem ide-induced natriuresis irrespective of salt intake, (b) antinatriures is is not affected by cilazapril, and (c) angiotensin II levels rise a fter furosemide on cilazapril in therapeutic doses.