Fasting induces a high level of 3-nitrotyrosine in the brain of rats.

Although the relationship between hyperglycemia (using diabetic animal model) and plasma nitrotyrosine level has been studied, the effect of hypoglycemia on nitrotyrosine level in the brain has not been addressed. Here, we evaluated nitration of protein, the colocalization of nitration with alpha-synuclein, activity of inducible nitric oxide synthase, and nitric oxide content using fasting and diabetic animal models. The results showed that signals of alpha-synuclein were widely distributed in most parts of the pallium, midbrain, hippocampus and cerebellum, as indicated by immunohistochemistry. Most signals of the 3-nitrotyrosine were colocalized with those of alpha-synuclein in the midbrain of fasting rats. The level of proteins containing 3-nitrotyrosine was significantly increased in the brain of fasting rats in Western blotting, especially in the midbrain, compared with control rats. In addition, the 3-nitrotyrosine signals increased in hippocampus of diabetic rats. Immunoprecipitation showed that alpha-synuclein was nitrated in the fasting rats. The iNOS activity and nitric oxide levels were significantly increased in both fasting and diabetic animals. The enhanced 3-nitrotyrosine level in the brain of fasting rats suggests that nitration of protein including alpha-synuclein in the midbrain is more affected by hypoglycemia in fasting than hyperglycemia in diabetic rats.