Progesterone regulation of epidermal growth factor receptor in rat deciduabasalis during pregnancy

Ovarian steroid hormones and epidermal growth factor (EGF) play important i nteractive roles in proliferation and decidualization of mesometrial stroma l cells during pregnancy. This study determined the ontogeny of EGF recepto r (EGF-R) expression in the decidua basalis (DB) throughout pregnancy and i ts regulation by estrogen and progesterone (P-4). DB were isolated from rat s between Days 8-21 of pregnancy and prepared for immunohistochemistry or W estern analysis. In one study, rats were ovariectomized (Ovx) on Day 8 or 9 and given estradiol-17 beta, P-4, or both. In another study, the antiproge stin, mifepristone (RU-486), was administered on Day 9. During normal pregn ancy, total EGF-R (phosphorylated and unphosphorylated forms) increased fro m Day 8 to a maximum level on Days 10 and 12. Tyrosine-phosphorylated EGF-R (pEGF-R), the bioactive form, was also highest on Days 10 and 12, Both for ms of receptor decreased to almost undetectable levels during DB regression on Days 17-21. Immunohistochemistry of DB from Ovx rats revealed that only P-4 was able to maintain normal expression of EGF-R; RU-486 decreased EGF- R expression within 6 h,and by 24 h EGF-R and pEGF-R were 15% of the Day 10 control group levels. These findings show that EGF-R is a P-4-dependent pr otein associated with stromal cell proliferation and decidualization.