The influence of enalapril or spironolactone on experimental cyclosporin nephrotoxicity.

Adult Sprague-Dawley rats treated daily for 14 days with 50 mg/kg cyclosporin A (CsA) exhibited nephrotoxicity, characterized by reduced glomerular filtration rate, decreased urinary sodium and potassium flow, tubular enzymuria and proximal tubular structural damage. Elevations in plasma renin activity (PRA) were observed on day 4, but returned to normal within 7 days. Co-treatment of animals for the 14 day period with enalapril (8 mg/kg/day), a potent inhibitor of angiotensin converting enzyme (ACE), or spironolactone (25 mg/kg/day), the distal tubular antagonist of aldosterone, reduced the nephrotoxicity, although PRA remained elevated. Neither enalapril nor spironolactone affected circulating CsA levels. These data suggest that the action of aldosterone on the distal tubule may be important in the pathogenesis of CsA nephrotoxicity.