Possible beneficial effects of melatonin supplementation on arsenic-induced oxidative stress in Wistar rats.

The effects of melatonin on arsenic-induced changes on cellular antioxidant system were studied in male rats of the Wistar strain. Arsenic treatment (i.p. as sodium arsenite) was done at a dose of 5.55 mg/kg body weight (equivalent to 35% of LD50) per day for a period of 30 days, while melatonin supplementation (i.p.) was performed at a dose of 10 mg/kg body weight per day for the last 5 days prior to sacrifice. Melatonin supplementation reversed the arsenic-mediated changes in reduced glutathione (GSH) level and lipid peroxidation in liver and kidney. Arsenic-induced decreased glutathione reductase activity in liver and increased activity in kidney was appreciably counteracted by melatonin. Melatonin also inhibited arsenic-induced free hydroxyl radical production in the tissues. The decreased superoxide dismutase (SOD) activity in liver and kidney and that of catalase in liver due to arsenic treatment were also counteracted by melatonin. It is suggested that melatonin acts as a protective agent against arsenic-induced cellular oxidative stress.