The influence of methylene blue and L-NAME on the development of streptozotocin-induced diabetes in rats.

The cytokine-induced overproduction of nitric oxide by immunocompetent cells with subsequent development of oxidative stress is suggested to be one of important pathophysiological mechanisms of the pancreatic beta cells damage in streptozotocin-induced experimental diabetes. The aim of our study was to compare the influence of two nitric oxide inhibiting compounds: methylene blue and L-NAME (N-omega-nitro-L-arginine-methyl ester) on the streptozotocin diabetes development and the oxidative stress parameters in male rats. Blood glucose, glycated haemoglobin, serum malondialdehyde concentration and erythrocyte superoxide dismutase activity were measured in control, diabetic (streptozotocin 70 mg/kg i.p.), methylene blue (50 mg/kg in the food), and diabetic group treated simultaneously with methylene blue (10 animals in each group). In the second experiment the L-NAME was used instead of methylene blue. It was found that both methylene blue and L-NAME partially suppressed the development of diabetes, but did not unambiguously influence the oxidative stress parameters. We conclude, that both methylene blue and L-NAME partially suppress the development of streptozotocin-induced diabetes in rats. The precise mechanism of this effect is not clear. We failed to demonstrate clear effect of methylene blue and/or L-NAME on oxidative stress development in diabetic rats.