Short term effects of acute inhibition of the angiotensin-converting enzyme on the renin-angiotensin system and plasma atrial natriuretic peptide in healthy dogs fed a low-sodium diet versus a normal-sodium diet.

The purpose of the present study was to quantify some of the short term responses of the renin-angiotensin system (RAS) to a recommended dosage of the angiotensin-converting enzyme inhibitor enalapril in clinically healthy dogs fed a normal-sodium and a low-sodium diet. A single dose of enalapril (0.5 mg/kg PO) was given to eight clinically healthy male Beagle dogs after a period where the dogs were fed a normal-sodium diet and low-sodium diet, respectively. Serum angiotensin-converting enzyme activity (ACE), plasma renin activity (PRA), plasma aldosterone concentration (PAC), and plasma atrial natriuretic peptide (ANP) concentration were measured during the following twenty-four hour period. The data indicate that enalapril induced a potent blockade of the renin-angiotensin system (RAS) for at least twenty-four hour. Specifically, enalapril during low-sodium diet elicited an exaggerated increase in PRA and a diminished decrease in ACE and ANP when compared to the results of the drug during normal-sodium diet. Long term controlled studies of enalapril in dogs with congestive heart failure (CHF) are warranted in order to determine the duration of action and optimal dose of enalapril.