Differential distribution of estrogen receptor-beta and estrogen receptor-alpha in the porcine ovary.

Steroids act on the follicle through autocrine and paracrine mechanisms to regulate follicular growth and steroidogenesis. Estradiol plays a significant role in determining the fate of the developing follicle and acts via specific receptors which are nuclear transcription factors. It has been established that besides classical estrogen receptor-alpha (ER alpha) novel forms termed ER beta exist. In species studied to date these two types of ERs exhibit different tissue localisation patterns and levels of expression. The present study was performed to determine whether ER alpha and ER beta are differentially expressed in the porcine ovary. Immunohistochemical studies using antibodies to ER alpha and ER beta, established the predominance of ER beta over ER alpha in the porcine ovary. Cyclical changes in estrogen receptor-beta expression were observed. The immunostaining was present in all types of follicles, and decreased in corpus luteum while it regressed. In the contrary estrogen receptor-alpha staining was seen only in large preovulatory follicle and in early corpora lutea.