The endometrium undergoes an indispensable differentiation process – decidualization in embryo-implantation. While the maternal-embryo cross-talk in initiating decidualization remains largely unknown, it has been cleared that the endometrial epithelium is required. Our previous studies have demonstrated that the endometrial epithelial expression of ENaC is enhanced during implantation and that intrauterine injection of ENaC blocker, amiloride, inhibits the implantation rate in mice, indicating the potential role of the epithelial ENaC in implantation. Interestingly, serine proteases, the reported ENaC activity-modulating factors, are known to be required for implantation and also, have been shown to promote the release of PGE2 from many epithelial cells, which has been demonstrated to play crucial roles in decidualization. Thus, we hypothesized that ENaC may be involved in the initiation of PGE2 release from endometrial epithelial cells leading to decidualization. In the present study, endometrial epithelial cells of mice were primarily cultured and grown on semipermeable membranes for forming polarized monolayers. Trypsin, a serine protease, aprotinnin, the protease inhibitor and amiloride, the ENaC blocker, were added to the culture medium, and the release of PGE2 to basolateral compartment was detected using an EIA kit. The results showed that, incubating with trypsin (20μg/mL) for 10 min could significantly enhance the PGE2 level in the treated cells as compared to the untreated control. While pretreated the cells with amiloride (10μM) or aprotinin (20µg/ml) for 30 min reversed the effect of trypsin. These results have demonstrated the involvement of ENaC in the release of PGE2 from endometrial epithelial cells, indicating its potential role in decidualization. Thus, ENaC appears to be essential to implantation.