Expression of estrogen receptor α and β genes in the mediobasal hypothalamus, pituitary and ovary during the canine estrous cycle

Abstract

Estrogen receptor α (ERα) and ERβ mRNA levels were measured in the mediobasal hypothalamus, the anterior pituitary and the ovary of beagle bitches at various stages of the estrous cycle. With polymerase chain reaction analysis we detected ERβ gene transcripts in all tissue samples. The levels of hypothalamic and pituitary ERα and β mRNAs increased from mid anestrus to proestrus and declined thereafter. In the ovary, ERα mRNA levels increased from proestrus to diestrus and were positively correlated with plasma progesterone levels ( r=0.62, P<0.01), whereas ERβ mRNA levels increased from mid anestrus to proestrus and were positively correlated with plasma estradiol-17β levels ( r=0.73, P<0.001). These results suggest that the rise in hypothalamic and pituitary ERα and β mRNAs is associated with termination of anestrus, and that increases in ovarian ERα and β mRNAs may be involved in initiating development of the follicle or corpora lutea.