Background: Lung injury occurs following lower limb reperfusion due to neutrophil infiltration and free oxygen radicals. Melatonin, the chief secretory product of the pineal gland, plays a role in the regulation of various physiological and neuroendocrine functions. In this study, injury in the lungs due to experimental lower extremity ischemia-reperfusion (I-R) and the protective effect of melatonin were investigated.

Methods: Forty male New Zealand white rabbits were used in the study. Rabbits were randomly divided into four groups: Group 1 (sham group, n=10), group 2 (I-R group without treatment, n=10), group 3 (preischemia treatment group, n=10), group 4 (prereperfusion treatment group, n=10). Only anesthesia was performed to rabbits in group 1 and after 6 hours blood and tissue samples were taken. In groups 2, 3 and 4, after anesthesia tourniquets were applied to bilateral hind limbs at the hip level. After 4 hours of ischemia, the tourniquets were removed and following two hours of reperfusion period, blood and tissue samples were taken. Melatonin (10 mg/kg) was administered intraperitoneally 15 minutes before ischemia to group 3, and 15 minutes before reperfusion to group 4. Plasma malondialdehyde (MDA) levels were measured in blood samples and lung tissue MDA levels were determined. Additionally, lung tissue was examined histopathologically.

Results: The levels of tissue and plasma MDA were found to be significantly lower in group 4 when compared to groups 2 and 3 (p<0.01). Histopathological examination revealed a lower neutrophil count, less interstitial edema and congestion in group 4 (p<0.01), in which the septums between the alveoli were also thinner.

Conclusion: Administration of melatonin before reperfusion decreased the lung injury caused by temporary lower extremity ischemia-reperfusion. Melatonin exerts these effects by inhibiting lipid peroxidation and neutrophil infiltration.

Keywords : Lung/pathology; melatonin/therapeutic use; reperfusion injury