Day and Night Effect of Single Dose of Ionising Radiation and Melatonin Treatment of Lung Tissue of Rats

Abstract

Objectives: We investigated the day-night differences in oxidative-injury and the inflammatory response in rat lung following total body irradiation by measuring thiobarbituric acid reactive substances levels and myeloperoxidase activity. Materials and Methods: 63 male rats were randomly divided into 6 groups and were exposed to a dose of 8 Gy to the total body region either in the morning or evening together with vehicle or melatonin administration, immediately before, immediately after and 24 h preceeding irradiation (10, 20 and 10 mg/kg, ip, respectively). Rats in the control group didn't receive any treatments. 48 h after irradiation, all animals were sacrificed. Results: Irradiation increased thiobarbituric acid reactive substances levels. Melatonin administration decreased both thiobarbituric acid reactive substances levels and myeloperoxidase activity when the time of irradiation is not taken into consideration. Depending on the time of irradiation, thiobarbituric acid reactive substances levels increased after total body irradiation only in morning group; treatment with melatonin significantly decreased thiobarbituric acid reactive substances levels. Total body irradiation did not increase myeloperoxidase levels but melatonin treatment in both time-points caused a significant decrease. Conclusion: The effect of melatonin can be attributed to its antioxidant and free radical scavenger properties. Although further studies are required to define underlying mechanism(s) of time dependent variations in thiobarbituric acid reactive substances levels in rats to which total body irradiation and total body irradiation plus melatonin were applied, this study might help to optimize the treatment time with irradiation.