The effect of cyclosporin (CS) on intrinsic glomerular level of antioxidants in puromycin aminonucleoside (PAN) nephrosis was examined. A single intravenous dose of PAN (50 mg/kg body weight) given to Sprague-Dawley rats resulted in marked proteinuria. Ten days after PAN injection, the rats were treated with daily intraperitoneal injection of CS (10 mg/kg body weight/day) for 10 days. PAN-treated rats without CS treatment (PAN rats) had significantly lower activities of glomerular superoxide dismutase (SOD) and catalase (CAT) than normal rats (p