Introduction: Reactive oxygen species (ROS) have important roles in the pathogenesis of ischemia reperfusion injury (I/R) of skeletal muscles Melatonin was proved to be an antioxidant agent and many experimental models showed that it reduces I/R injury in many tissues. The objective of present study was to detect protective antioxidant effect of melatonin on I/R injury of skeletal muscles.

Material and Methods: Albimino wistar rats were randomly allocated into 3 groups. There were 8, 10, 10 rats in sham, I/R and I/R + melatonin (Mel) groups respectively. Right hind limb ischemia was achieved by clamping femoral arteries in all groups except for control group. Melatonin (10 mg/kg) was administered intraperitoneally in I/R + Mel group 48, 24, 1 hour before reperfusion. After a period of 2 hour ischemia followed by 1.5 hour reperfusion, muscles and venous blood samples were collected for biochemical analysis and histopathological examination. Plasma antioksidant enzyme activities of süperoxide dismutase (SOD), glutathion peroxidase (GSH-Px), and levels of MDA and NO. were investigated. Enzyme activities of catalase (CAT), protein carbonyl (PC), SOD, GSH-Px and levels of MDA and NO. were analysed in muscle tissues.

Results: Antioxidant enzyme activities and levels of MDA and NO. in plasma were significantly higher in I/R group compared to control group (p< 0,001). Muscle tissues of I/R groups revealed significant higher antioxidant enzyme activity and MDA, NO. levels with respect to control group (p< 0,001). Levels of these parameters in muscle and plasma revealed significant reduction in I/R + Mel group with respect to I/R group (p< 0.001). Histopathological examination of ischemic muscles in I/R group showed significant degeneration and inflammation compared to control group whereas melatonin administered ischemic muscles showed significant reduction of degeneration and inflammation with respect to I/R group (p< 0.001).

Conclusions: Levels of NO. and MDA and antioxidant enzyme activity were significantly higher and also revealed significant degeneration and inflammation in I/R group. These results support the opinion that ROS is an important factor in the pathogenesis of I/R injury in skeletal muscles. We attribute the increasing enzyme activities in I/R group to a compensatory mechanism against ROS. Levels of NO. and MDA and antioxidant enzyme activity in tissue and plasma of I/R + Mel group were significantly lower and additionally revealed significant improvement in inflammation and degenaration. This proves the potential ROS scavenging effect of melatonin in reduction of I/R injury. In conclusion we suggest that melatonin may be used in the treatment of I/R injury due extremity injuries with vascular compromise, extremity surgery with prolonged tourniquet time and compartment syndrome.