DUAL EXPRESSION OF PROLACTIN-RELATED PROTEIN IN DECIDUA AND TROPHOBLAST TISSUES DURING PREGNANCY IN RATS

Decidual prolactin-related protein (dPRP) is a member of the prolactin gene family and is abundantly expressed in the rat deciduum. Previous ly, dPRP was shown to associate with heparin-containing molecules and was found to reside, at least in part, within the decidual extracellul ar matrix, where it was postulated to influence decidual cells and oth er cell types. The purpose of this investigation was to identify the c ellular origin and the temporal and regional characteristics of dPRP e xpression in the rat uterus during pregnancy. Protein expression was e valuated by Western blot analysis, immunoprecipitation, and immunocyto chemistry; dPRP mRNA expression was assessed by reverse transcriptase polymerase chain reaction and in situ hybridization. Decidual PRP was first detected at Day 6 of pregnancy or pseudopregnancy. Expression in creased with the growth of the deciduum and then declined coincident w ith regression of decidual tissue. Throughout the first half of pregna ncy 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 chorioallant oic placenta. Trophoblast giant cells and spongiotrophoblast cells wit hin the junctional zone of the chorioallantoic placenta expressed dPRP , as did the Rcho-1 trophoblast cell line. In conclusion, dPRP product ion is elevated from implantation until parturition through the partic ipation of decidual (early pregnancy) and trophoblastic (late pregnanc y) tissues.