The influence of NO synthase inhibitor and free oxygen radicals scavenger methylene blue on streptozotocin-induced diabetes in rats

The excessive production of nitric oxide (NO) and the subsequent increase o f local oxidative stress is suggested as one of the pathophysiological mech anisms of streptozotocin-induced diabetes. It was reported that the adminis tration of NO synthase inhibitors partially attenuated the development of s treptozotocin-induced diabetes and reduced hyperglycaemia. Here we have stu died the influence of methylene blue, which combines the properties of NO s ynthase inhibitor with antioxidant effects. The experiments were performed on male rats divided into four groups: control diabetic (single dose of 70 mg of streptozotocin/kg i.p.), methylene blue (50 mg/kg in the food) and di abetic simultaneously fed with methylene blue. After 45 days the experiment s were discontinued by decapitation. Serum glycaemia, glycated haemoglobin and oxidative stress parameters (plasma malondialdehyde concentration and e rythrocyte superoxide dismutase activity) were significantly higher in the diabetic group. Simultaneous methylene blue administration partially reduce d glycaemia and glycated haemoglobin, but did not decrease oxidative stress . We conclude that NO synthase inhibitor methylene blue partially attenuate s the development of streptozotocin-induced diabetes in male rats, but does not reduce the development of oxidative stress in the diabetic group.