The predictive value of enzymuria in cyclosporin A-induced renal toxicity in the rat.

The acute nephrotoxic properties of cyclosporin A (CsA) were investigated in normotensive, adult male Sprague-Dawley rats. Animals received either 50 or 100 mg CsA/kg by gastric intubation for 7 days. Within 24 h, significant increases in urinary N-acetyl-beta-D-glucosaminidase (NAG) and gamma-glutamyl transpeptidase (gamma GT) activity were observed at both doses of CsA. Renal function abnormalities, however, were not apparent until 2 days (100 mg/kg) or 7 days (50 mg/kg). Progressive increases in enzymuria were evident in both groups between 1 and 4 days, at which later time proximal straight tubular cell damage was first observed. The data obtained using this model clearly demonstrate that enzymuria provides a sensitive index of acute CsA-induced renal cell damage and that enzymuria precedes detectable renal functional and structural abnormalities.