Evidence for the presence of the estrogen receptor in the ovary of the baboon (Papio anubis)

Abstract

Although intraovarian estrogen has been firmly established as an important factor in the regulation of ovarian follicular development and function in the rat, an autocrine-paracrine role for estrogen in the primate ovary is not yet established. Immunocytochemical identification of an estrogen receptor in the monkey follicle was negative, but it was positive for the granulosa cells of antral follicles of the human ovary. In the present study baboon ovaries obtained during the follicular phase were examined for the presence of estrogen receptor by immunocytochemical analysis of frozen sections and Northern blot analysis of RNA extracts of the ovaries. Immunocytochemistry identified the estrogen receptor in the granulosa cells of healthy appearing and atretic or cystic-like antral follicles and in occasional, but rare, thecal cells. The ovaries contained a prominent mRNA species for the estrogen receptor, approximately 7 kilobases in size, which was present in relatively low abundance compared to that in the nonpregnant baboon uterus, but in a similar abundance to the estrogen receptor mRNA content of the pregnant endometrium. These studies are the first to report the presence of estrogen receptor mRNA in the ovary of a primate. These results in conjunction with the immunocytochemical studies firmly establish the presence of the estrogen receptor in the primate ovary and suggest an autocrine-paracrine role for intraovarian estrogen in primate ovarian physiology.