Dual expression of prolactin-related protein in decidua and trophoblast tissues during pregnancy

Decidual prolactin-related protein (dPRP) is a member of the prolactin gene family and is abundantly expressed in the rat de-ciduum. Previously, dPRP was shown to associate with heparin-containing molecules and was found to reside, at least in part, within the decidual extracellular matrix, where it was postulated to influence decidual cells and other cell types. The purpose of this investigation was to identify the cellular origin and the tem-poral and regional characteristics of dPRP expression in the rat uterus during pregnancy. Protein expression was evaluated by Western blot analysis, immunoprecipitation, and immunocyto-chemistry; dPRP mRNA expression was assessed by reverse tran-scriptase polymerase chain reaction and in situ hybridization. Decidual PRP was first detected at Day 6 of pregnancy or pseu-dopregnancy. Expression increased with the growth of the de-ciduum and then declined coincident with regression of deci-dual tissue. Throughout the first half of pregnancy or pseudo-pregnancy, dPRP and mRNA were predominantly localized to the antimesometrial deciduum of the developing conceptus. During the second half of gestation, expression also appeared in the chorioallantoic placenta. Trophoblast giant cells and spongiotrophoblast cells within the junctional zone of the cho-rioallantoic placenta expressed dPRP, as did the Rcho-1 tropho-blast cell line. In conclusion, dPRP production is elevated from implantation until parturition through the participation of de-cidual (early pregnancy) and trophoblastic (late pregnancy) tis-sues