科研之友
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摘要
Around day 12 of gestation, the porcine embryo undergoes a dramatic morphological change in which the trophectoderm elongates and begins producing and secreting estradiol-17汕. Placental size in late gestation is related to the size of the embryo at the time of elongation. Embryos of the Chinese Meishan secrete approximately one-half the amount of estradiol-17汕 produced by embryos of domestic large white breeds. Larger litters with smaller, more efficient placentae are associated with the Chinese Meishan. Meishans treated with estradiol-17汕 at the time of elongation exhibited an increased placental size. The aim of this study was to determine the effects of treatment with exogenous estradiol-17汕 at the time of elongation on the proliferation of the trophectoderm of the embryo, as well as the changes in uterine luminal growth factors, hormones and ions. Pregnant gilts (N = 12) were randomly selected to receive either estradiol-17汕 or vehicle every 6 h for 48 h, beginning on day 12 of gestation. On day 14, embryos and uterine luminal contents were surgically collected. The proliferation index of the trophectoderm and the concentrations of growth factors, hormones and ions were determined. Estradiol-17汕 treatment resulted in a doubling of the proliferation index. There was an increase in PGE2 and PGF2汐 in the uterine flushings of treated gilts. There were no changes in the concentrations of estradiol-17汕, IGF-1 or calcium. In conclusion, treating gilts with estradiol-17汕 resulted in a doubling of the proliferation rate in the trophectoderm and likely an increased length of the embryo at elongation.
