Biochemical and Histological Study of Protective Effect of Sodium Tungstate on Oxidative Stress Induced by Streptozotocin in Pancreas of Diabetic Rats

Purpose: The aim of this study was evaluation of effects of sodium tungstate on oxidative stress in pancreas of streptozotocin induced diabetic rats. Materials and Methods: Sixty mature Wistar male rats (Age: 2-3 month) were selected and divided into six groups randomly (n=10). Control (C), STZ-induced diabetic (D), STZ-induced diabetic rats were treated by sodium tungstate (1 mg/ml) in drinking water at one week before induction of diabetes and throughout the experiment (TDB), food-restricted diabetic group (FRD) with an equal amount of food as that consumed by the TDB group, healthy control rats treated with sodium tungstate (TC), diabetic rats treated with sodium tungstate from one week after STZ administration (TDA). Food and fluid intake of all above rat groups were measured daily and bodyweight, blood glucose and insulin were measured every week. At the end of the treatment period (five weeks after induction of diabetes) after overnight fast, all animals were sacrificed under light ether anesthesia. Immediately, blood samples were collected from tail vein. Glucose levels were measured by oxidase-peroxidase enzyme method, and serum insulin levels were determined by ultra sensitive rat insulin kit, using ELISA. The pancreas was quickly removed and a piece of it placed in cold saline solution used to determination of antioxidant power. The lipid peroxidation product (MDA) was measured in nanomoles of MDA-TBA complex. The thiobarbitiuric acid reactive substances (TBRAS) were expressed per milligram of tissue protein. Antioxidant power of blood and pancreas were measured by ferric reducing/antioxidant power (FRAP). Another portion of pancreas was fixed in modified Lilli’s solution. fter tissue blocking in paraffin 4 µm thick sections prepared and was stained for granulated beta-cells by the modified aldehyde fuchsin method. Stained section examined by light microscope. One-way analysis of variance (ANOVA) followed by Tukey´s post hoc test for multiple comparisons were used to compare differences between experimental groups. Significant level was set at p< 0.05. Results: Blood glucose levels of TDB group were lower than D, TDA, and FRD groups (p< 0.01); and were comparable with control rats in the period of treatment. Blood insulin levels of TDB, TDA, D and FRD rats were lower than C and TC rats (p<0.01). In addition, blood and pancreas antioxidant power were increased in TDB rats in comparison with D, TDA and FRD groups (p<0.01). Likewise, blood and pancreas lipid peroxidation were decreased in TDB rats than D, TDA and FRD groups (p< 0.01). Histological study showed that granulated beta cells in TDB rats were greater than D, TDA and FRD groups. Conclusion: Results demonstrate that sodium tungstate can reduce oxidative stress and increase antioxidant power in blood and pancreas of rats. Thus, Sodium tungstate treatment before STZ injection can preserve pancreatic beta cells from STZ-induced damages.