Oxygen free radicals have been suggested to be a contributory factor in diabetes complications. The aim of this study was to examine the effects of gyburide oil the antioxidant enzyme activities in the heart tissue of diabetic rats. We investigated the activities of antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase) in the hearts of both control and streptozotocin-induced diabetic rats. In the heart of diabetic rats, the activity of total superoxide dismutase decreased significantly (p < 0.005), whereas the activity of catalase and glutathione peroxidase increased to a large extent (p < 0.0001 and p = 0.05, respectively) at the end of the fourth week compared with the control group. Glyburide treatment of diabetic rats for 4 weeks corrected the changes observed in diabetic heart. In addition, blood glucose levels of untreated diabetic rats decreased following the glyburide treatment. These results demonstrate that the sudfonylurea glyburide is capable of exerting direct insulin-like effect on heart superoxide dismutase, catalase and glutathione peroxidase activities of diabetic rats in vivo. (C) 2004 Prous Science. All rights reserved.