Diabetes mellitus is a significant risk factor for cardiovascular complications. Experimental evidence suggests that oxidative stress plays a dominant role in the pathogenesis of diabetes mellitus. This study was undertaken to investigate the effect of vanadyl sulfate on blood glucose, serum and tissue lipid profiles and on stomach and spleen tissues in STZ-induced diabetic rats. In this study, male 6-6.5-month-old Swiss albino rats were used. Rats were randomly divided into four groups. Group I: control animals (normal, nondiabetic animals) (n = 13); Group II: vanadyl sulfate controls (n = 5); Group III: streptozotocin (STZ)-diabetic, untreated animals (n = 11); and Group IV: STZ diabetic animals given vanadyl sulfate (n = 11). Experimental diabetes was induced by intraperitoneal (i.p.) injection of STZ in a single dose of 65 mg kg(-1) body weight. Vanadyl sulfate was administered by gavage at a dose of 100 mg kg(-1). The levels of cholesterol, phospholipid, high density lipoprotein-cholesterol (HDL-) low density lipoprotein-cholesterol (LDL-), very low density lipoprotein-cholesterol (VLDL-), triglycerides and lipid peroxidation (LPO) in serum and cholesterol in liver were assayed according to standard procedures. The levels of lipid peroxidation, glutathione (GSH) and nonenzymatic glycosylation (NEG) in stomach and lipid peroxidation and glutathione (GSH) in spleen tissues were analyzed. After 60 days of treatment, serum cholesterol, LDL-cholesterol, triglyceride, phospholipid, VLDL-cholesterol, LPO, blood glucose levels, stomach LPO and NEG, spleen LPO significantly increased, but serum HDL-cholesterol, stomach GSH and spleen GSH levels significantly decreased in the diabetic group. On the other hand. treatment with vanadyl sulfate reversed these effects. These results reveal that diabetes mellitus increased oxidative damage in stomach and spleen tissues and vanadyl sulfate has an ameliorating effect on the oxidative stress via its antioxidant property. The administration of vanadyl sulfate may be able to reduce hyperglycemia and hyperlipidemia related to the risk of diabetes mellitus. (c) 2005 Elsevier Ltd. All rights reserved.