Renal Structure and Function in Rats After Suprapharmacologic Doses of Quinapril, an Angiotensin-Converting Enzyme Inhibitor

Angiotensin-converting enzyme (ACE) inhibitors have adverse effects on renal function in some hypertensive patients, and some of them produce renal tubular lesions in animals at high doses. To assess the effect of quinapril on renal function and structure, a 4-week time-course study was conducted in male Wistar rats with daily oral gavage doses of 0, 10, 100, or 400 mg/kg. Glomerular filtration rate (GFR) estimated as creatinine clearance and fractional electrolyte excretion values were derived from urinalysis and blood chemistry data obtained at days 1, 7, 14, and 28. Renal sections were collected on these days for histopathologic evaluation, and cortical slices were obtained to assess organic ion transport in vitro. Expected pharmacologic effects of an ACE inhibitor were observed at all doses and included increased urine output, increased water consumption, decreased serum aldosterone (65 or 25% of control at 10 or 400 mg/kg, respectively, on day 28), increased plasma renin activity (PRA, up to two- to threefold higher than controls at day 28), and hypertrophy of the juxtaglomerular apparatus. Despite these expected class effects, quinapril administration to male rats for 28 days produced no functional alterations or renal tubular lesions suggestive of renal toxicity at doses up to 400-fold higher than the effective antihypertensive dose in rats.