MERCURIC CHLORIDE-INDUCED REACTIVE OXYGEN SPECIES AND ITS EFFECT ON ANTIOXIDANT ENZYMES IN DIFFERENT REGIONS OF RAT-BRAIN

The present study was undertaken to determine if in vitro exposure to mercuric chloride produces reactive oxygen species (ROS) in the synapt osomes prepared from various regions of rat brain. The effects of in v ivo exposure to mercury on antioxidant enzymes such as superoxide dism utase (SOD) and glutathione peroxidase (GPx) activities in different r egions of rat brain were also investigated. Adult male Sprague-Dawley (CD) rats were dosed with 0, 1, 2.0 or 4.0 mg HgCl2/kg body weight, fo r 7 days. One week after the last dose, animals were sacrificed by dec apitation, their brains were removed and dissected and frozen in dry i ce prior to measuring the activities of these enzymes. The results dem onstrated that in vitro exposure to mercury produced a concentration-d ependent increase of ROS in different regions of the rat brain. In viv o exposure to mercury produced a significant decrease of total SOD, Cu ,Zn-SOD and Mn-SOD activities in the cerebellum of rats treated with d ifferent doses of mercury. SOD activity did not vary significantly in cerebral cortex and brain stem. GPx activity declined in a dose-depend ent manner in the cerebellum with a significant reduction in animals r eceiving the 4 mg HgCl2/kg body weight. The activity of GPx increased in the brain stem while unchanged in the cerebral cortex. The results demonstrate that inorganic mercury decreased SOD activity significantl y in the cerebellum while GPx activity was affected in both cerebellum and brain stem. Therefore, it can be concluded that oxidative stress may contribute to the development of neurodegenerative disorders cause d by mercury intoxication.