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영어

Estrogen is essential for reproductive processes such as maturation of ovarian follicles, embryo implantation, placentation, lactation, parturition, sexual differentiation, and sexual behavior in females. Generally estrogen binds to nuclear receptors, estrogen receptor alpha (ERα) and beta (ERβ). Recently, novel estrogen receptor, G protein- coupled estrogen receptor 1 (GPER1), has been identified and shown to be expressed in the plasma membrane. However, the expression and regulation of GPER1 has not been determined in the female reproductive system in pigs. Thus, this study determined the expression of GPER1 in the endometrium during the estrous cycle and pregnancy in pigs. We obtained endometrial tissues from gilts on day (D) 0, D3, D6, D9, D12, D15 and D18 of the estrous cycle and on D12, D15, D30, D60, D90 and D114 of pregnancy, and chorioallantoic tissues on D30, D60, D90 and D114 of pregnancy. GPER1 mRNA was expressed in the endometrium during the estrous cycle and pregnancy in pigs. During the estrous cycle, GPER1 expression was higher in diestrus and proestrus than in estrus and metestrus. During pregnancy, GPER1 mRNA was high during the preimplantation period and low during mid- to late pregnancy. Expression of GPER1 was significantly higher on D15 of the estrous cycle than D15 of pregnancy. RT-PCR analysis showed that GPER1 mRNA was not detectable in conceptus on D12 and D15 of pregnancy. In chorioallantoic tissues, GPER1 mRNA increased toward term pregnancy. Endometrial explant culture study showed that the expression of GPER1 mRNA was down-regulated by increasing doses of progesterone but not affected by estradiol. In situ hybridization analysis showed that GPER1 mRNA was localized to luminal epithelial cells in the endometrium on D15 of estrous cycle. These results indicate that GPER1 mRNA is expressed in the endometrium during the estrous cycle and pregnancy in a stage- and pregnancy status-dependent manner, suggesting that GPER1 may play an important role in mediating estrogen actions of the maternal-fetal interface in pigs. Further analysis of signaling pathway and function of GPER1 in the reproductive system is needed.