TURKISH JOURNAL OF BIOCHEMISTRY-TURK BIYOKIMYA DERGISI, cilt.33, sa.3, ss.104-110, 2008 (SCI-Expanded)
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.