ABSTRACT
Ionizing radiation interacts with biological systems to induce excessive fluxes of free radicals that attack various cellular components. Melatonin has been shown to be a direct free radical scavenger and indirect antioxidant via its stimulatory actions on the antioxidant system. The aim of this study was to evaluate the antioxidant role of melatonin against radiation-induced oxidative injury to the rat liver after whole body irradiation. In this experimental study, thirty-two rats were divided into four groups. Group 1 was the control group, group 2 only received melatonin [30 mg/kg on the first day and 30 mg/kg on the following days], group 3 only received whole body gamma irradiation of 10 Gy, and group 4 received 30 mg/kg melatonin 30 minutes prior to radiation plus whole body irradiation of 10 Gy plus 30 mg/kg melatonin daily through intraperitoneal [IP] injection for three days after irradiation. Three days after irradiation, all rats were sacrificed and their livers were excised to measure the biochemical parameters malondialdehyde [MDA] and glutathione [GSH]. Each data point represents mean ñ standard error on the mean [SEM] of at least eight animals per group. A one-way analysis of variance [ANOVA] was performed to compare different groups, followed by Tukey's multiple comparison tests [p<0.05]. The results demonstrated that whole body irradiation induced liver tissue damage by increasing MDA levels and decreasing GSH levels. Hepatic MDA levels in irradiated rats that were treated with melatonin [30 mg/kg] were significantly decreased, while GSH levels were significantly increased, when compared to either of the control groups or the melatonin only group. The data suggest that administration of melatonin before and after irradiation may reduce liver damage caused by gamma irradiation