Progestin, estrogen, and insulin-like growth factor-I stimulate the prolactin receptor mRNA in human endometrial stromal cells.

OBJECTIVE

To identify the expression of the prolactin receptor (PRL-R) mRNA in human endometrial stromal and glandular epithelial cells in order to ascertain the autocrine/paracrine actions of PRL and to determine the effect of steroid hormones and growth factor on PRL-R mRNA during decidualization.

METHODS

Human endometrial stromal cells and glandular epithelial cells were isolated from tissue fragments by collagenase digestion and total RNA was isolated. Stromal cells were cultured with or without progesterone (P) or medroxyprogesterone acetate (MPA) for various periods of time. Prolactin receptor and its mRNA were determined by Western blot analysis and solution hybridization/ribonuclease protection assay. The effects of estrogen, insulin-like growth factor (IGF)-I, and PRL on PRL-R mRNA were also studied.

RESULTS

Both types of endometrial cells expressed PRL-R mRNA. Prolactin receptor mRNA content in glandular cells was consistently much less than that in stromal cells (1 versus 5-12). Progesterone or MPA stimulated the PRL-R mRNA expression two- to greater than ten-fold in the stromal cells of eight endometrial specimens. Stimulation by progestin was concentration dependent and required at least 1-2 days' incubation. A high level of PRL-R mRNA was maintained in stromal cells beyond 10 days' incubation with progestin. The stimulatory effect of progestin was inhibited by RU 486 and by cycloheximide, suggesting that progestin-receptor interaction and de novo protein synthesis mediate the up-regulation. In addition, estradiol and IGF-I stimulated PRL-R mRNA. Western blot analysis showed that progestin increased the PRL-R protein. A 90-kd band previously identified as PRL-R was ubiquitously distributed in the soluble and particulate fractions of the stromal cells.

CONCLUSION

This study demonstrated that PRL-R mRNA is expressed in both types of endometrial cells and that PRL-R mRNA and its protein are up-regulated by progestin, estrogen, and IGF-I during decidualization of endometrial stromal cells.