Use of Melatonin to Prevent Selenite-Induced Cataract Formation in Rat Eyes

Abstract

Purpose: To evaluate effects of melatonin on sodium selenite-induced cataract formation. Methods: Twenty-three Sprague-Dawley rat pups were randomized into three groups. Group 1(n = 9), injected with selenite (s.c.) on postpartum day 10; group 2 (n = 7), injected with selenite (s.c.) on day 10 plus melatonin (i.p.) on days 8–15; group 3 (n = 7), saline-injected controls. Development of cataract was assessed weekly under a dissection microscope. Rat lenses and serums were analyzed for antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT); oxidative stress indicators xanthine oxidase (XO) and malondialdehyde (MDA), a marker of lipid peroxidation; and protein carbonyl (PC), a marker of protein oxidation. Results: Significant differences (p < 0.05) were seen in cataract development by the three groups. All rats developed dense nuclear cataract in group 1. Dense nuclear cataract was not observed in group 2: five of seven rats developed minor cataracts, while the other two had clear lenses. In control rats (group 3), all lenses remained clear. In selenite group (group 1), lens and serum levels of MDA, PC, and XO were significantly higher and levels of SOD and CAT were significantly lower than those in control group (p < 0.001). In selenite+melatonin group (group 2), lens and serum levels of MDA, PC, and XO significantly decreased and levels of SOD and CAT significantly increased when compared with selenite group. Conclusions: Studies with the rat selenite cataract model strongly support the activity of melatonin as an endogenous antioxidant and anticataract agent.