ObjectiveTo study the expression of zonula occluden-1 (ZO-1) in ileum tissues and the possible mechanism of intestinal mucosal barrier injury in rats with severe acute pancreatitis (SAP). MethodsFifty SD male rats were randomly divided into sham operation group and SAP group, then SAP group was divided into four subgroups with 10 rats in each subgroup according to the sampling time of 3, 6, 12, and 24 h. The SAP model was made by injecting 5% bovine sodium deoxycholate into biliarypancreatic duct with Aho’s method. The rats were killed at 3, 6, 12, and 24 h after making model. The rats in the sham operation group were killed directly. Tumor necrosis factor-α (TNF-α), diamine oxidase (DAO), and histological changes in pancreatic and intestinal pathologies were observed. At the same time, the ZO-1 protein and mRNA expressions of ileum tissues were detected by immunohistochemistry and RT-PCR, respectively. ResultsCompared with the sham operation group 〔TNF-α: (10.83±0.96) ng/L; DAO: (354.79±3.67) U/L; ZO-1 protein: (10.40±0.45) score; ZO-1 mRNA: 0.878±0.014 8〕, the levels of TNF-α at different time 〔3 h: (125.30±0.94) ng/L; 6 h: (181.89±4.93) ng/L; 12 h: (230.58±1.28) ng/L; 24 h: (198.89±4.83) ng/L〕 were significantly higher (Plt;0.05), the activities of DAO 〔3 h: (235.77±0.67) U/L; 6 h: (117.22±5.58) U/L; 12 h: (106.69±1.39) U/L; 24 h: (91.18±1.09) U/L〕 were significantly lower (Plt;0.05), ZO-1 protein 〔3 h: (8.70±0.22) score; 6 h: (3.73±0.19) score; 12 h: (3.92±0.22) score; 24 h: (4.29±0.30) score〕 and mRNA (3 h: 0.806±0.020 7; 6 h: 0.370±0.015 8; 12 h: 0.502±0.019 2; 24 h: 0.562±0.030 3) expressions of the ileum tissues were significantly lower (Plt;0.05) in the SAP group; Meanwhile, the necrosis of ileum mucous membrane chorioepithelium, angiorrhexis and hemorrhage, and inflammatory cell infiltration in the pancreatic and ileum tissues were also observed. ConclusionThe decrease of expression of ZO-1 in ileum tissues is one of the vital causes for mucosal barrier injury in SAP, probably through acts the excessive release of inflammatory cytokines TNF-α and the decrease of DAO activity.