UP-REGULATION OF THE HUMAN PROLACTIN RECEPTOR IN THE ENDOMETRIUM

In humans, uterine endometrial stromal cells differentiate (decidualiz e) into decidual cells that express prolactin (PRL). Decidual PRL expr ession continues throughout pregnancy, thus decidual cells lining feta l membranes of term placenta synthesize and secrete PRL. To examine th e hypothesis that PRL may play an autocrine role in the decidual cells , we examined the expression of the PRL receptor (PRL-R) during in vit ro decidualization of stromal cells and in term decidua. In endometria l stromal cells decidualized by treatment with 1 mu M medroxyprogester one and 10 nM estradiol for 3, 6, and 9 d, respectively, a 12.7 kb PRL -R transcript increased 3-3.5-fold, 16.5-17-fold, and 23.5-24-fold, re spectively, compared with untreated controls, in duplicate experiments . Progesterone-dependent PRL-R and PRL expression were stimulated by 1 mu M prostaglandin E(2). Term decidua expressed the longform of the P RL-R and five major PRL-R transcripts (12.7, 9.7, 7.0, 3.6, and 2.8 kb ). In contrast, human liver expressed two major transcripts (12.7 and 9.7 kb) while HepG2 cells expressed a single 7.0-kb-sized transcript. These studies demonstrate that PRL-R expression is stimulated upon pro gesterone-induced PRL gene expression in endometrial stromal cells sup porting the hypothesis that PRL may have an autocrine effect in the en dometrium and decidua.