Physiological roles of estrogen and TGF-α in the maintenance of pregnancy

怀孕及其维持对于家畜的繁殖是必不可少的。本研究旨在阐明雌激素和转化生长因子-α在妊娠过程中的生理作用，最终目的是促进家畜妊娠率的提高。在妊娠早期生产盐酸法洛唑(FAD)会延迟大鼠着床前胚胎的发育、胚胎的带状带脱落以及对蜕皮化刺激最敏感的时期。由于治疗推迟了1~2天开始着床，推测雌激素可能会刺激胚胎发育，并为着床做好子宫准备。妊娠晚期持续应用FAD可降低血浆雌激素浓度，增加子宫赖氨酰氧化酶(LO)的mRNA表达，而LO是形成胶原分子内和分子间交联所必需的。治疗使S的…降低子宫组织结构更加坚固和顺应性更强，宫内压力增加4倍，导致约四分之一的胎儿受伤。提示雌激素可抑制子宫LO的表达，为妊娠晚期快速生长的胎儿维持良好的生理环境。另一方面，在绵羊着床过程中，转化生长因子-α及其受体在胚胎和子宫内膜中均有表达，推测转化生长因子-α可能具有促进胚胎生长、调节子宫内膜细胞增殖和分化的作用。此外，还观察到转化生长因子-α和表皮生长因子受体在犬子宫内膜中的表达，并推测它们可能参与了子宫内膜上皮细胞的增殖、分化和退化。雌激素还调节子宫LO的表达，使子宫的生理状态适合于致命的生长。此外，子宫中表达的转化生长因子-α可能在胚胎生长和子宫内膜细胞的增殖、分化和退化中发挥重要作用。较少

Pregnancy and its maintenance are essential for reproduction of farm animals. This study was performed to clarify the physiological roles of estrogen and TGF-α in pregnancy, and the final objective is to contribute towards the increase of pregnancy rates in farm animals.Continuous treatment with an inhibitor of estrogen. production, fadrozole hydrochloride (Fad), during early pregnancy delayed preimplantation embryo development, zona shedding by embryos and the period of maximum sensitivity to a decidualizing stimulus in rats. Since the treatment delayed the initiation of implantation by 1 or 2 days, it was speculated that estrogen might stimulate the embryo development and prepare the uterus for implantation. Continuous treatment with Fad during late pregnancy reduced the concentration of plasma estrogen and increased the uterine mRNA expression of lysyl oxidase (LO), which is necessary for the formation of intra-and inter-molecular cross-links of collagen. The treatment reduced the s … More ize and compliance of the uterine tissue framework and increased the intrauterine pressure by 4-fold to cause injuries in about one-quarter of fetuses. These results suggest that estrogen inhibits uterine expression of LO and keeps the physical environment suitable for the rapidly growing fetuses in late pregnancy. On the other hand, expression of TGF-α and its receptor (EGF-R) in the embryo and endometrium was found in the ovine implantation process, and it was speculated that TGF-α might stimulate the embryo growth and regulate proliferation and differentiation of endometrial cells. Furthermore, expression of TGF-α and EGF-R was observed in the canine endometrium, and the possibility of their involvement in the proliferation, differentiation and regression of endometrial epithelial cells was suggested.In conclusion, estrogen enhances the embryo growth and regulates the proliferation, difforentiation and regression of endometrial cells, resulting in establishment of implantation. Estrogen also regulates uterine expression of LO and keeps the uterine physical states suitable for fatal growth. Furthermore, TGF-α expressed in the uterus may play important roles in the embryo growth and the proliferation, differentiation and regression of endometrial cells. Less