Endocrinology of the Transition from Recurring Estrous Cycles to Establishment of Pregnancy in Subprimate Mammals

Abstract

Pregnancy is established and maintained in subprimate mammals in response to a series of interactions among the conceptus (embryo and associated membranes), uterus, and/or ovarian corpus luteum (CL). These interactions prevent functional and structural regression of the CL, or luteolysis. This chapter describes aspects of the endocrinology of recurring estrous cycles in ruminants, swine, horses, cats, dogs, and rodents, but the primary focus is on signaling for maternal recognition of pregnancy. During the peri-implantation period, pregnancy recognition signals from the conceptus to the maternal system are anti-luteolytic and/or luteotrophic. The functional life-span of the CL is controlled by release of prostaglandin F2α (PGF) from the uterus and/or ovaries, whereas pregnancy recognition signals from the trophoblast may act in a paracrine or endocrine manner to interrupt endometrial or intraovarian production of luteolytic PGF (antiluteolytic) or the effect may be directly on the CL (luteotropic). The primary focus of this chapter is pregnancy recognition signals in subprimate mammals, which prevent luteolysis and ensure maintenance of an intrauterine environment that supports events associated with establishment and maintenance of pregnancy.