The antioxidant effect of melatonin in lung injury after aortic occlusion-reperfusion

Acute aortic occlusion with subsequent ischemia-reperfusion of the lower extremities is well known to predispose to lung injury. Melatonin (MEL), a pineal hormone, is a free radical scavenger and an antioxidant. The purpose of this study was to assess the putative protective role of MEL in lung ischemia-reperfusion injury induced by aortic occlusion-reperfusion. Thirty-two rats were randomly allocated to four groups as follows: SHAM (Sham Laparotomy), SHAM+MEL, Aortic Ischemia Reperfusion (AIR) and AIR+MEL. Twenty mg/kg live weight MEL was given intraperitoneally 1 h prior to the experiment. An atraumatic microvascular clamp was placed across the infrarenal abdominal aorta (IAA) just after its origin from the aorta for 30 min. The microvascular clamp on IAA was removed and reperfused for 12 h. Lung tissues were assessed for malondialdehyde (MDA) level and myeloperoxidase (MPO) activity. MDA level and MPO activity, indicating the extent of lipid peroxidation and neutrophil infiltration of lung, respectively, significantly increased in AIR group when compared to SHAM and SHAM+MEL groups (P<0.05). Treating rat with MEL significantly decreased MDA levels as well as MPO activity in AIR+MEL group when compared to AIR group (P<0.05). In this study, exogenously administered MEL reduced lung injury after aortic occlusion reperfusion.