Koc, M., Taysi, S., Buyukokuroglu, M. E. and Bakan, N. The Effect of Melatonin against Oxidative Damage during Total-Body Irradiation in Rats. Radiat. Res. 160, 251–255 (2003).

Melatonin has been reported to participate in the regulation of a number of important physiological and pathological processes. Melatonin, which is a powerful endogenous antioxidant, may play a role in the prevention of oxidative damage. The aim of this study was to investigate the effect of pretreatment with melatonin (5 mg kg^–1 and 10 mg kg^–1) on γ-radiation-induced oxidative damage in plasma and erythrocytes after total-body irradiation with a single dose of 5 Gy. Total-body irradiation resulted in a significant increase in plasma and erythrocyte MDA levels. Melatonin alone increased the levels of SOD and GSH-Px. Erythrocyte and plasma MDA levels in irradiated rats that were pretreated with melatonin (5 or 10 mg kg^–1) were significantly lower than those in rats that were not pretreated. There was no significant difference between the effects of 5 and 10 mg kg^–1 on plasma MDA activities and CAT activities. However, erythrocyte MDA levels showed a dose-dependent decrease, while GSH-Px activities increased with dose. Our study suggests that melatonin administered prior to irradiation may protect against the damage produced by radiation by the up-regulation of antioxidant enzymes and by scavenging free radicals generated by ionizing radiation.