EXPRESSIONS OF ESTROGEN RECEPTORS ALPHA AND BETA ARE REGULATED BY PROSTAGLANDIN F2ALPHA, TUMOR NECROSIS FACTOR ALPHA, AND INTERFERON GAMMA IN BOVINE LUTEAL CELLS

Abstract

Estradiol (E) functions in gene regulation by binding to a specific intracellular receptor. Although E receptors α (ERα) and β (ERβ) are known to be present in bovine corpus luteum (CL), the functions of ERs throughout the luteal phase and the mechanisms that control ER expressions in luteal cells are not fully understood. To determine possible functions of ERα and ERβ and to clarify the regulatory mechanisms of ER expressions in the bovine CL, we examined 1) changes in the protein expressions of ERs in CL during the luteal phase, and 2) the effects of prostaglandin (PG) F2α, tumor necrosis factor α (TNFα) or interferon γ (IFNγ) on ER mRNA expressions in cultured bovine luteal cells. Western blot analyses revealed that ERα and ERβ proteins were expressed throughout the luteal phase. ERα protein level was higher at the early luteal stage (Days 2–3 after ovulation) and mid luteal stage (Days 8–12) than at the other luteal stages. ERβ protein level was higher at the developing and mid luteal stages than at the other luteal stages. The ratio of ERβ to ERα was higher in the regressed stage than in the other stages. Luteal cells obtained from mid stage CL (Days 8–12) were incubated with PGF2α (3.5–350 ng/ml), TNFα (0.25–2.5 ng/ml) or IFNγ (0.25–2.5 ng/ml) for 24 h. PGF2α and TNFα inhibited ERα and ERβ mRNA expressions. IFNγ suppressed ERβ mRNA expression but did not affect the expression of ERα mRNA. These data suggest that PGF2α, TNFα, and IFNγ regulate ERα and ERβ expressions in bovine luteal cells. The overall findings lead us to hypothesize that, in cow, ERα plays roles in maintenance of CL function, while ERβ functions in luteolysis. (poster)