Abstract: Objective To investigate the effect of melatonin post-intervention on the expression of thioredoxin-1(TRX-1) in rats with acute necrotizing pancreatitis(ANP). Methods Male Spraque-Dawley rats were randomly allocated to control group, ANP group，melatonin post-intervention group with 24 rats in each group .The rats in ANP group received three intraperitoneal injections of 25 ml/kg body weight 6%L-arginine at an interval of 1 h to induce ANP. The rats in melatonin post-intervention group received intraperitoneal injections of 20ml/kg body weight 0.25% melatonin after ANP induction. Rats in control group received intraperitoneal injections of same amount of saline. Rats were sacrificed at 6, 12 and 24 h after ANP induction. The pathological evaluation of pancreatic tissues was performed. The concentrations of malondialdehyde and myeloperoxidase in pancreatic tissues were measured. The serum level of TRX-1 was measured by ELISA. The expressions of thioredoxin-1 and thioredoxin-1mRNA in pancreatic tissues were confirmed by immunohistochemistry and RT-PCR, respectively.Results Comparerd to the control group, pathological scores, malondialdehyde ,and myeloperoxidase of pancreatic tissues in ANP group were significantly increased(p < 0.05),while they in melatonin post-intervention group were significantly lower (p < 0.05) than those in ANP group. Comparerd to the control group,serum TRX-1 contents in ANP group significantly decreased(p < 0.05) at 6- and 12 h points, while they in melatonin post-intervention group were significantly higher (p < 0.05) than those in ANP group. the peak value of TRX-1 protein and TRX-1mRNA expressions in pancreatic tissues shifted from 12 h after ANP induction in ANP group to 6 h after ANP group in melatonin post-intervention group.Conclusions Melatonin post-intervention reduced the injury of pancreatic tissue may be through increased tissue and serum TRX-1 levels in ANP rats.

Key words: Acute necrotizing pancreatitis, melatonin, thioredoxin-1