Effects of the angiotensin converting enzyme (ACE) inhibitor, captopril, on the cardiovascular, endocrine, and renal responses to furosemide in conscious lambs.

To test the hypothesis that angiotensin II modulates the physiological responses to furosemide in the newborn, various parameters of cardiovascular, renal, and endocrine function were measured before and after iv injection of furosemide to eight conscious, chronically instrumented lambs in the presence and absence of the angiotensin converting enzyme (ACE) inhibitor, captopril. During ACE inhibition, the rise in heart rate and decrease in renal blood flow in response to furosemide did not occur, and the natriuretic and diuretic responses to furosemide were attenuated by approximately two-thirds. There was also an increase in the urinary excretion of prostaglandin F2 and prostaglandin F1 alpha as well as an increase in the excretion of prostaglandin E2 after furosemide, in the presence of ACE inhibition. Therefore, the cardiovascular, renal, and endocrine responses to furosemide in conscious lambs were significantly altered by ACE inhibition.