Objective   To study the effect of ulinastatin on transcript and translation of ENaC-β mRNA and protein of human alveolar epithelial A549 cells treated with TNF-α and its mechanism of action in treatment of acute respiratory distress syndrome.    Methods   A549 cells were divided into normal control group

ulinastatin group

TNF-α group and ulinastatin + TNF-α group. TNF-α concentration was 100 ng/ml. A549 cells in each group were treated with ulinastatin，TNF-α or ulinastatin + TNF-α for 6

12 and 24 h

respectively. A549 cells in ulinastatin and ulinastatin + TNF-α groups were treated with ulinastatin at the concentration of 1 250

2 500 and 5 000 U/ml for 12 h

and then at the concentration of 5 000 U/ml for 6 and 24 h

respectively. ENaC-β mRNA and protein expression levels were measured by semi-quantitative RT-PCR and Western blotting.    Results   No significant difference was found in effect of ulinastatin on ENaC-β mRNA and protein expression level in A549 cells in 6

12 and 24 h after treatment with it between treatment group and control group（P0.05）. The ENaC-β mRNA and protein expression level in A549 cells in 6

12 and 24 h after treatment with ulinastatin (at the concentration of 5 000 U/ml) + TNF-α was significantly increased compared with that after treatment with TNF-α (P0.01）. However

it was significantly different 12 h after treatment with different concentrations of ulinastatin + TNF-α from that after treatment with TNF-α alone（P0.01）. The ENaC-β mRNA and protein expression level was different at different time points after treatment with different concentrations of ulinastatin + TNF-α（P0.05）.    Conclusion   Ulinastatin can not directly up-regulate the transcription and translation of ENaC-β in A549 cells

but can reverse the inhibitory effect of inflammatory response on ENaC-β expression in a concentration-dependent manner.