Immunohistochemical localization of estrogen receptors ERα and ERβ in the spiny mouse (Acomys cahirinus) ovary during postnatal development

This study was designed to determine the expression pattern of estrogen receptor (ER) subtypes in the Acomys cahirinus ovarian cells during its postnatal development. Immunohistochemical studies revealed the presence of ER alpha and ER beta in germinal epithelium cells and interstitial tissue. Both these ER subtypes were also seen in granulosa cells and oocytes of growing follicles, however, the level of ER beta expression was higher in comparison with ER alpha. In contrast to ER beta, ER alpha protein was also present in theca cells. The expression of ERs increased with animals' age, but it decreased during follicular maturation. Moreover, the immunolocalization of ER subtypes in luteal cells showed that not ER beta, but ER alpha expression is upregulated throughout corpus luteum development. These immunohistochemical studies demonstrate, for the first time, that ER alpha is also expressed in the mouse granulosa cells and it may be a mediator of estrogen action in granulosa cells proliferation and differentiation.