Abstract: AIM: To clarify the effects of melatonin on acute necrotizing pancreatitis (ANP)associated lung injury and the expressions of macrophage migration inhibition factor (MIF)and TNF-αin the lung of rats. METHODS: A total of 36 SD rats were randomly divided into sham operation group(SO), acute necrotizing pancreatitis group (ANP) and melatonin group (MT).ANP was induced by the injection of sodium taurocholate into the pancreatic duct.Rats inMT group were injected intraperitoneally with MT 30 min before the induction of ANP.Rats were sacrificed at 4 and 24 hours after the induction of ANP(n =6 for each time point).RT-PCR was used to measure the mRNA levels of MIF and TNF-αin the lung.Immunohistochemistry analysis was performed on the lung tissues to detect MIF.The histopathological changes of the pancrea and the lung were also observed. RESULTS: Compared with the SO group. the pancreatic and pulmonary pathological changes in ANP group and MT group were significantly aggravated. the mRNA levels of MIF and TNF-αin the lung were markedly up-regulated(P<0.05), Compared with the ANP group. the pulmonary and pancreatic pathological changes in MT group were alleviated. the mRNA levels of MIF and TNF-αin the lung of MT group were decreased significantly (P<0.05).Positive immunostaining for MIF was observed predominantly within the bronchial epithelial cells in the lung. CONCLUSION: MIF may play an important role in the pathogenesis of ANP associated lung injury. MT can reduce its expression and alleviate the lung injury.

Key words: acute necrotizing pancreatitis, lunginjury, macrophage migration inhibition factor, melatonin