Sample preparation and biochemical assays

All blood samples were allowed to clot at room temperature and centrifuged at 2,000 g for 10 min to harvest serum. Serum biochemical parameters of BUN, and Scr and CK levels were measured (n = 12 per group) using the commercially available kits, BUN (995–17711), Scr (991–32593), and CK (994–64291), all from Wako Pure Chemical Industry, Japan.

The kidneys were excised, then washed in ice-cold saline and homogenized in 0.1 M Tris–HCl buffer (pH 7.4). The homogenate were first centrifuged at 10,000 g for 15 min and the supernatants were then centrifuged at 100,000 g for 1 h. The resulting supernatant (cytosolic fraction) was used for the determination of enzymatic activities and lipid peroxidation. Kidney biochemical parameters of SOD, MDA and GSH-Px were measured spectrophotometrically (Eon, BioTeK, USA) using the commercially available kits, SOD (A001-1), MDA (A003-1), and GSH-Px (A005), all from Jiancheng Bioengineering Institute, Nanjing, China.