ABSTRACT
<p><b>AIM</b>To investigate the protective effect of melatonin (MT) on lung tissues during acute lung injury (ALI) in rats and its possible mechanism.</p><p><b>METHODS</b>All rats were randomly divided into four groups: control group, lipopolysaccharide (LPS) group, dexamethasone (DEX) and MT treatment group. Myeloperoxidase (MPO) activity, superoxide dismutase (SOD) activity and malonaldehyde (MDA) content of lung tissues were detected at 3, 6 and 12 h after intratracheal instillation in each group. In addition, the expression of intercellular adhesion molecule-1 (ICAM-1) were observed through immunohistochemistry staining in lung tissues.</p><p><b>RESULTS</b>Compared with control group, SOD activity decreased significantly in LPS group (P < 0.01), but MPO activity,MDA content and the expression of ICAM-1 increased obviously (P < 0.01). The administration of MT and DEX mitigated above changes significantly (P < 0.05 or P < 0.01).</p><p><b>CONCLUSION</b>MT possessed protective effect on lung tissues during ALI through scavenging free radicals and inhibiting the expression of ICAM-1 probably.</p>