Partial protection against streptozotocin-induced hyperglycaemia by superoxide dismutase linked to polyethylene glycol.

To test the possible role of superoxide radicals in the diabetogenic action of streptozotocin, blood glucose levels were measured in mice after a single high-dose (150 mg/kg body weight) or multiple low-dose (40 mg/kg for 5 days) injections of streptozotocin. Pretreatment 6 h before streptozotocin with 250-300 mg/kg superoxide dismutase coupled to polyethylene glycol reduced the hyperglycaemic response in mice injected with a single dose of streptozotocin. The blood glucose levels after multiple low doses of streptozotocin were not affected by superoxide dismutase-polyethylene glycol. Enzymatically inactive superoxide dismutase did not affect the development of hyperglycaemia. The results suggest that superoxide radicals may play a role in the diabetogenic action of streptozotocin injected as a high-dose single bolus.