EXPRESSION OF PARATHYROID HORMONE-RELATED PROTEIN MESSENGER-RNA BY UTERINE TISSUES AND EXTRAEMBRYONIC MEMBRANES DURING GESTATION IN RATS

Hybridization histochemistry and solution hybridization studies were p erformed to localize the expression of parathyroid hormone-related pro tein (PTHrP) during implantation in rats. Parallel studies were perfor med on rat uteri bearing oil-induced deciduomata and on cultured blast ocysts. PTHrP mRNA begins to be expressed at day 5.5 of gestation by t he uterine epithelium in the anti-mesometrial crypts marking the sites of implantation and in comparable regions during induction of deciduo ma. Trophoblastic giant cells express the gene as soon as they are phe notypically recognizable both in vivo and in culture, but PTHrP mRNA c annot be detected in the early blastocyst or in cells of the inner cel l mass. Decidual cells produce PTHrP mRNA both in normal gestation and after the induction of deciduomata. In each case, the expression of t he gene in decidual cells follows its expression in uterine epithelium by 48 h. The uterine topographical location and time of expression