Male Wistar rats were killed 1, 2, or 4 days after a single intraperitoneal injection of cisplatin (5 mg/kg). Functional renal indices, enzymatic activities, and morphological variables were studied. One day after the injection, the treated group showed an increase in the magnesium and phosphate fractional urinary excretion (FE) vs the control group (FE Mg = 5.2 +/- SEM 0.5% vs 13.0 +/- 1.7%; P less than 0.01; and FE P = 4.7 +/- 0.7% vs 14.0 +/- 1.9%; P less than 0.01). Two days after cisplatin administration, a decrease in creatinine clearance of treated animals was found, to 0.33 +/- 0.03 vs 0.51 +/- 0.03 ml/min; P less than 0.05. Na-K-ATPase and ouabain-insensitive ATPase activities were studied in the proximal convoluted tubule, the medullary thick ascending limb of the Henle's loop (mTAL), and the distal convoluted tubule. Only in mTAL one day after the cisplatin injection was there a decrease in Na-K-ATPase activity in the treated group vs controls (1103 +/- 145 vs 1734 +/- 189 pmol Pi/mm.h; P less than 0.05). Morphological studies showed a decrease in mTAL diameters on day 1, and an increase in proximal convoluted tuble diameters at day 2 of treated rats vs controls, at 27.8 +/- 0.6 vs 31.4 +/- 0.7 microns; P less than 0.05, and 50.4 +/- 1.2 vs 47.4 +/- 0.2 microns; P less than 0.05 respectively.(ABSTRACT TRUNCATED AT 250 WORDS)