Expression of estrogen receptor α (ERα) and estrogen receptor β (ERβ) in the ovarian follicles and corpora lutea of pregnant swine

The objective of the study was to demonstrate the presence of estrogen receptor α (ERα) and β (ERβ) protein and corresponding mRNA in porcine ovarian follicles and corpora lutea obtained on day 10, 18, 32, 50, 71 and 90 post coitum (p.c.) using immunohistochemistry, Western blot, and RT-PCR analysis. Immunohistochemistry showed that ERα protein was located in the granulosa cells of ovarian follicles and the strongest immunoreaction was observed on days 32 and 50 p.c. The ERβ protein was found mainly in theca cells of follicles as well as in luteal cells. The most intense immunoreaction was observed on day 18 p.c. within theca cells, while in the corpus luteum (CL) the intensity of ERβ staining gradually increased and remained elevated at mid and late pregnancy. In CL by day 50 p.c. immunoreaction for ERβ was present only in small luteal cells, but starting from day 71 to 90 p.c. it was observed in both small and large luteal cells. Western blot analysis was performed and validated data obtained from immunohistochemistry. RT-PCR results indicated that ERα mRNA was expressed only in ovarian follicles of the pregnant swine, while that of ERβ in both follicles and CL. The results suggest an autocrine/paracrine role of estrogens acting via both ERα and ERβ in the regulation of the ovarian function during pregnancy and for the process of successful reproduction.