Effect of melatonin against oxidative stress in ultraviolet-B exposed rat lens

Purpose. To investigate the defensive effect of melatonin against oxidative stresses in ultraviolet-B (UVB) radiation induced cataract development. Methods. Young rats received 8 kJ/m(2) UVB for 15 min. For the intervention of cataract development intraperitoneal injection of melatonin (4 mg/kg da ily for 1 week) following UVB exposure was performed. Lenticular glutathion e peroxidase (GSHPx), catalase (CAT), superoxide dismutase (SOD) activities and glutathione (GSH), malondialdehyde (MDA) levels were determined in UVB -melatonin, UVB, and control groups. Results. One week after exposure in the UVB group, lens opacities were obse rved and CAT, SOD, and GSHPx activities, and GSH level were lower than cont rol and MDA level was higher than control (p < 0.05). In the UVB-melatonin group CAT and SOD activities were lower than control (p < 0.05), and the MD A level was lower than the UVB group (p < 0.05). Conclusions. These results suggest that melatonin may protect against the U VB-induced cataract development by directly quenching lipid peroxides and i ndirectly by enhancing the production of the endogenous antioxidant GSH.