To explore the potential role of monocyte chemotactic protein 1 (MCP-1) and macrophage inflammatory protein 2 (MIP-2) in the pathogenesis of acute necrotizing pancreatitis (ANP), and to study the effect of N-acetylcysteine (NAC) on the mRNA expression of MCP-1 and MIP-2.Thirty-five SD rats were randomly divided into 3 groups: sham-operation (SO) group (n = 5), acute necrotizing pancreatitis (ANP) group (n = 15), and NAC-pretreated group (n = 15), ANP were induced by retrograde injection of 4% sodium taurocholate into the biliopancreatic duct. The NAC- groups underwent intraperitoneal injection of NAC 500 mg/kg 30 minutes before the induction of sodium taurocholate. The ANP and NAC groups were re-divided into 3 equal subgroups respectively: 3 h, 6 h, and 12 h subgroups. 3, 6, and 12 hours after the establishment of models heart blood samples were collected from 5 rats from each model group to detect the serum amylase. Then the rats were killed by blood letting with their pancreases taken out. HE staining and microscopy were used to observe the pathological changes of the pancreas. The wet/dry ratio of pancreas was determined. Enzyme histochemical method was used to detect the activity of myeloperoxidase (MPO) in the pancreas. RT-PCR was used to examine the mRNA expression of MCP-1 and MIP-2.The levels of serum amylase, wet/dry ratio of pancreas, pancreatic MPO activity, and histological score of pancreas of the ANP group increased time-dependently, all the levels at different time-points were significantly higher than those of the SO group (all P < 0.01). The expression levels of MCP-1 mRNA at the time points 3, 6, and 12 h of the ANP group were 0.3653 +/- 0.0213, 0.5890 +/- 0.0225, and 0.7164 +/- 0.0275 respectively, all significantly higher than that of the SO group (0.1492 +/- 0.0036, all P < 0.01). The expression levels of MIP-2 mRNA at different time points of the ANP group were 0.3871 +/- 0.0286, 0.6040 +/- 0.0448, and 0.7692 +/- 0.0620 respectively, all significantly higher than that of the SO group (0.1593 +/- 0.0117, all P < 0.01). The intrapancreatic MPO levels at the time points 3 h, 6 h, and 12 h of the NAC group were 0.63 +/- 0.03, 0.88 +/- 0.05, and 1.31 +/- 0.09 respectively, all significantly lower than those of the ANP groups (0.89 +/- 0.03, 1.42 +/- 0.14, and 1.94 +/- 0.07, all P < 0.05). The MCP-1 mRNA expression levels at different time points the NAC group were 0.2497 +/- 0.0168, 0.4457 +/- 0.0097, and 0.6306 +/- 0.0423 respectively, and the MIP-2 mRNA expression levels at the time points 3 h, 6 h, and 12 h of the NAC group were 0.2436 +/- 0.0099, 0.4312 +/- 0.0221, and 0.6302 +/- 0.0288 respectively, all significantly lower than those of the ANP group (all P < 0.05). The pancreatic histological scores at different time points of the NAC group were 3.50 +/- 0.61, 5.60 +/- 0.65, and 7.50 +/- 0.79, all significantly lower than those of the ANP group (5.10 +/- 0.42, 7.50 +/- 0.50, and 9.90 +/- 0.96, all P < 0.05). The MCP-1 mRNA expression and MIP-2 mRNA expression were both correlated with the severity of pancreatic injury (r = 0.76 and 0.82, both P < 0.05).The chemokines of MCP-1 and MIP-2 are overexpressed at the early stage of acute pancreatitis. Both of them may play an important role in the pathogenesis of AP. NAC may have beneficial effects on AP through downregulation of the expression of MCP-1 and MIP-2.