Abstract: Objective  To investigate the protective effect and mechanism of ulinastatin (UTI) on intestinal epithelial cell barrier. Methods  Caco2 cells were cultured， epithelial cells monolayer models induced by  tumor necrosis factorα（TNFα ）  were established and were randomly divided into blank control group， TNFα model group， lowdose UTI group (50  000 U/kg)， middledose UTI group (100  000  U/kg) and highdose UTI group (200 000  U/kg). The transepithelial electrical resistance (TER) and fluoresce  in isothiocyanate marked dextran FITCdextran in all groups were determined by Millicell electrical resistance meter and multifunctional plate reader.  Interleukin 6 (IL6) and  IL10 were determined by enzymelinked immunosorbent assay (ElISA). The apoptosis rate was measured by flow cytometry， and the expression of tight junction protein occludin and ZO1 were measured by Western blot. Results  The expression of TER， FITCdextran， occludin and ZO1 were significantly lower in TNFα model group than those in blank control group， while IL6， IL10 and apoptosis rate were significantly higher (P<0.05). After  UTI  treatment，  TER， FITCdextran， occludin and ZO1 were significantly higher than those in  TNFα model group， while IL6， IL10 and apoptosis rate were significantly lower (P<0.05).  UTI  change  in highdose group was the most significant (P<0.05). Conclusion   UTI may protect the intestinal epithelial cell barrier injury induced by TNFα through inhibiting the release of inflammatory mediators and regulating the expression of tight junction associated proteins.

Key words: intestines, cell mucosal barrier, tumor necrosis factoralpha, ulinastatin, tight junction protein