We investigated the in vitro effects of citrulline (0.1, 2.5 and 5.0 mM) and ammonia (0.01, 0.1 and 1.0 mM), and the influence of resveratrol (0.01 mM, 0.1 mM and 0.5 mM) on pyruvate kinase, citrate synthase, succinate dehydrogenase (SDH), complex II, and cytochrome c oxidase activities in cerebral cortex, cerebellum and hippocampus homogenates of 60-day-old male Wistar rats. Results showed that 2.5 and 5.0 mM citrulline decreased pyruvate kinase activity in cerebral cortex and, at a concentration of 5.0 mM, increased its activity in hippocampus. Additionally, 5.0 mM citrulline increased citrate synthase activity in the cerebellum of rats. Citrulline (5.0 mM) reduced complex II and cytochrome c oxidase activities in cerebral cortex and hippocampus. With regard to ammonia, at 0.1 and 1.0 mM, decreased complex II activity in cerebral cortex and at 1.0 mM decreased its activity in cerebellum and hippocampus. Ammonia (1.0 mM) also decreased cytochrome c oxidase activity in cerebral cortex and cerebellum of rats. Resveratrol was able to prevent most of the alterations caused by these metabolites in the biomarkers of energy metabolism measured in the cerebrum of rats. Data suggest that these alterations in energy metabolism, caused by citrulline and ammonia, are probably mediated by the generation of free radicals, which can in turn be scavenged by resveratrol.
Keywords: Ammonia; Cerebrum; Citrulline; Citrullinemia Type I; Energy metabolism; Resveratrol.