The overall objective of this proposal is to gain further insight into the secretion and action of decidual luteotropin, a prolactin- like hormone secreted by the decidual tissue of pregnant and pseudopregnant rats. The first aim will be to establish a direct action of decidual luteotropin on luteal and follicular steroidogenesis. For this investigation, follicles and luteal cells will be either perifused with medium flowing from a decidual cell perifusion, or will be incubated with highly purified hormone. Using in vitro and in vivo approaches, we will investigate the possibility that decidual luteotropin acts locally on decidual and neighboring trophoblastic cells to control glycogen production by the decidua, and steroidogenesis by trophoblastic cells. The third specific aim is designed to determine the ontogeny of decidual luteotropin production throughout the life span of the decidual tissue. To date, with the exception of women and rats, it is not known whether the production of a PRL-like substance is a hormonal function of the decidual tissue. The last aim of this study will be to determine whether in other species in which decidualization accompanies implantation, prolactin-like hormones are produced by the decidual tissue. This would establish the decidua as an endocrine gland in species with hemochorial placentation. We will also investigate the possibility that in some of these species, decidual prolactin possesses luteotropic activity.