Implantation and Establishment of Pregnancy in the Pig.
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Establishment of pregnancy in the pig is initiated through the release of estrogens from the rapidly elongating conceptuses. Release of estrogens from the developing conceptuses alters the movement of endometrial prostaglandin F2 from being released into the vasculature (endocrine secretion) to sequestering in the uterine lumen (exocrine secretion). Rapid trophoblast elongation, which is unique to the pig, may be triggered through production of interleukin 12 (IL1B2) by conceptuses. Trophoblast elongation through the uterine horns provides the mechanism to allow conceptus-endometrial interactions essential for the implantation, placentation, and maintenance of pregnancy in the pig. This chapter provides current information on conceptus signaling pathways and endometrial responses to those conceptus factors leading to establishment of pregnancy.