Effects of melatonin on the levels of antioxidants and lipid peroxidation products in rats treated with ammonium acetate.

The antioxidant potential of melatonin (MLT) on hyperammonemia (induced by ammonium acetate treatment) were studied in rats. The levels of circulatory ammonia, urea and non-protein nitrogen increased significantly in ammonium acetate treated rats and decreased significantly in rats treated with melatonin and ammonium acetate. In brain tissues, the same pattern of alterations across groups was observed in the levels of thiobarbituric acid reactive substances and lipid profile variables (free fatty acids, triglycerides, phospholipids, and cholesterol). Further, enzymatic (superoxide dismutase, catalase and glutathione peroxidase) and non-enzymatic (reduced glutathione) antioxidants in brain tissues decreased significantly in ammonium acetate treated rats and increased significantly in rats treated with melatonin and ammonium acetate. These biochemical alterations could be due to the ability of melatonin to (i) scavenge a variety of radicals and reactive oxygen species (ii) induce antioxidative enzymes which reduce steady state levels of reactive oxygen species and (iii) stabilize cell membranes which assist them in reducing oxidative damage and thus could prevent oxidative stress in rats.