Localization of estrogen receptors in rhesus monkey ovary

We have previously demonstrated that the exogenous administration of estradiol-17β (E₂) to rhesus monkeys induces atresia of the dominant preovulatory follicle (DF); and that this effect is mediated centrally, via the inhibition of follicle-stimulating hormone, and is also exerted directly at the level of the ovarian granulosa cell. We wished to investigate whether the local effect of E₂ is transduced through interaction with the nuclear receptor for estrogen, particularly in light of certain evidence that suggests a general lack of estrogen receptor (E-R) in the rhesus monkey ovary, except in the germinal epithelium. In the present study, we evaluated the presence of E-R by both autoradiographic and immunocytochemical techniques. Frozen sections of ovaries from rhesus females were incubated in experiment 1 with either ³H-E₂ or ¹²⁵I-E₂, in the presence or absence of excess, non-radioactive ligand or analogues diethylstilbestrol (DES) or the receptor antagonist 4-OH-tamoxifen (TAM). ³H-E₂ binding was most intense over functional corpora lutea, and was reduced to background with excess DES; label was also evident over antral follicles, Image analysis showed specific binding of ¹²⁵I-E₂ by ovaries. In experiment 2, cryostat sections were processed for immunocytochemical staining using the per-oxidase-anti-peroxidase (PAP) method and the H222 monoclonal antibody to the E-R. Intense, specific label was observed over nuclei of germinal epithelium, but, additionally, for the first time, to granulosa cells of antral follicles and other compartments of the ovary. In this paper, we report the first evidence for estrogen binding to rhesus monkey ovary; tins binding is specific, apparently receptor mediated, and corroborated independently by autoradiographic and immunocytochemical means. We herein provide substantial support for estrogen's dramatic effects being exerted directly at the level of the monkey ovary. © 1993 Wiley-Liss, Inc.