To investigate the role of superoxide dismutase(SOD) in the pathogenesis of cadmium-induced acute nephrotoxicity.

Rats treated with a single intraperitoneal injection of cadmium(as CdCl2, 1 mg/kg) were included in the cadmium-treated group; the control group comprised untreated rats. 24-hour urine samples were obtained prior to sacrifice on days 1, 2, 4, 8 and 16(N = 10 per group), respectively. The activity of SOD and concentration of cadmium were measured in the homogenates of the renal cortex. Nephrotoxicity indices such as N-acetyl-beta-D-glucosaminidase(NAG) activity, total protein, and 24-hour urine volume, and the cadmium concentrations in the urine were measured.

The cadmium injection caused a significant increase of cadmium concentration in the renal cortex on days 1 and 2, and in the urine on days 1, 2 and 4. The NAG activities and total protein concentrations in urine were significantly increased on days 1, 2 and 4, and on days 1, 4 and 8, respectively. The peak values of NAG activity and total protein in urine were observed on days 1 and 4, respectively. A significant decrease of 24- hour urinary volume was induced on day 1. Renal SOD activity was significantly inhibited on day 1. Finally, on day 8, SOD activity was significantly increased and all nephrotoxicity indices except urinary total protein returned to the control level.

These results suggest that cadmium induces initial depression of SOD enzyme activities in the renal cortex followed by a later activation, and that the initial depression of this enzyme plays an important role in mediating the proteinuric injury of cadmium-induced acute nephrotoxicity.