Effects of quinidine on renal biochemistry and function in young and old rats.

Nephrotoxic effects of quinidine in male Fischer-344 rats in ages of 3-4 months and 20-22 months were evaluated. Renal cortical slice oxygen consumption, accumulation of p-aminohippurate and tetraethyl ammonium were inhibited in vitro. No age-related differences were observed. Quinidine decreased respiratory control index and ADP/O ratio in both age groups. Quinidine administration at 75 mg/kg/day for four days reduced tetraethylammonium transport in both young and old. Blood urea nitrogen increased in the old, but not in the young rats. Serum creatinine levels were elevated in both age groups. Renal cortical slice oxygen consumption decreased in the young but not in the old rats after quinidine administration. No changes in RCI or ADP/O ratio were observed in the two age groups. The results indicate that Fischer-344 rats in the ages of 20-22 months are not increasingly susceptible to quinidine-induced nephrotoxicity.