ABSTRACT
Secretin, a gastrointestinal peptide, has been found to be expressed in mouse endometrial stromal cells (mESCs) during early pregnancy. In order to further investigate the function of secretin during embryo implantation, the expression levels of secretin, secretin receptor, cytosolic phospholipase A(cPLA) and membrane prostaglandin E synthase 1 (mPGEs-1) were detected in the mice uterus from day 4 to 8 of pregnancy by real-time PCR, ELISA and in situ hybridization. mESCs isolated and cultured from day 4 of pregnancy were transfected with secretin expression vectors or treated with H89, a PKA inhibitor. Then the expression levels of cPLA, mPGEs-1 and cAMP responsive element-binding protein (CREB) were detected by real-time PCR and Western blot. The concentration of prostaglandin E2 (PGE) in the supernatant was determined by ELISA. The result showed that secretin, cPLAand mPGEs-1 mRNA expression increased gradually in implantation sites from day 5 to day 7 of pregnancy with the same tendency. The secretin levels in serum were significantly higher on days 6, 7 and 8 of pregnancy than that on day 5 of pregnancy. The concentration of secretin was significantly higher in implantation sites on days 6, 7 than that in non-implantation site on day 5. Transfection of secretin expression vector promoted cPLA, p-cPLAand mPGEs-1 expressions in mESCs, but not PGElevel in the supernatant. H89 could effectively inhibit the expression of CREB, p-CREB, p-cPLAand cPLAinduced by secretin. The results showed that the increased secretin expression in mESCs during embryo implantation may promote p-cPLA, cPLAand mPGEs-1 expression, and the promotion may be through PKA signaling pathway.