Expression of estrogen receptor at (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 at (ER alpha) and beta (ER beta) 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 ER alpha protein was located in the granulosa cells of ovarian follicles and the strongest immunoreaction was observed on days 32 and 50 p.c. The ER beta 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 ER beta staining gradually increased and remained elevated at mid and late pregnancy. In CL by day 50 p.c. immunoreaction for ER beta 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 ER alpha mRNA was expressed only in ovarian follicles of the pregnant swine, while that of ER beta in both follicles and CL. The results suggest an autocrine/paracrine role of estrogens acting via both ER alpha and ER beta in the regulation of the ovarian function during pregnancy and for the process of successful reproduction. (c) 2008 Elsevier Inc. All rights reserved.