Impaired antioxidant status in diabetic rat liver. Effect of vanadate.

In vivo effects of vanadate on the antioxidant status of control and alloxan diabetic rats liver were examined. The increased oxidative stress during diabetes caused a decline in the activities of glutathione peroxidase (GPx), catalase (CAT), CuZn superoxide dismutase (CuZn-SOD) and Mn-superoxide dismutase (Mn-SOD) in the liver. Reduced glutathione (GSH) was also depleted, but the level of oxidized glutathione and glutathione reductase activity remained unchanged in the livers of diabetic rats. Vanadate treatment of diabetic rats (0.6 mg/mL in drinking water) resulted in almost complete restoration of GPx and Mn-SOD but caused only a partial restoration of CuZn-SOD. However, CAT and GSH were found to be lowered further in vanadate-treated diabetic rats as compared to untreated diabetic rat. Similar decreases in CAT and GSH levels were also observed in the vanadate-treated controls. These results suggest that vanadate, an insulin-mimetic agent, effectively normalized hyperglycemia, but unlike insulin, could not completely restore the altered endogenous defence mechanisms in diabetic liver.