Potassium homeostasis during angiotensin-converting enzyme inhibition with enalapril

The effect of angiotensin-converting enzyme (ACE) inhibition on renal and extrarenal potassium (K) regulation was examined. Six healthy men were studied in double-blinded crossover fashion on placebo or enalapril, 80 mg/day. On day 4, the subjects were given an intravenous infusion of KCl and on day 5 an oral dose of 10% NH₄Cl. Treatment with enalapril decreased plasma aldosterone and increased plasma renin activity (PRA), epinephrine and norepinephrine, but did not affect serum glucose, plasma insulin or basal plasma K. Maximal increases in plasma K during K infusion or NH₄Cl ingestion were similar during enalapril and placebo treatment. With enalapril treatment urinary K excretion was unchanged following K loading but moderately reduced following NH₄Cl loading. We conclude that ACE inhibition does not acutely impair K homeostasis in men with normal renal function.