Immunocytochemical Localization of Estradiol and Progesterone Receptors in the Monkey Ovary Throughout the Menstrual Cycle*

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Abstract
Both estradiol and progesterone may act locally to modulate ovarian function in various species. This study examined the distribution of estradiol and progesterone receptors (ER and PR, respectively) within the primate ovary throughout the menstrual cycle. Ovaries were collected from rhesus or cynomolgus monkeys during the early, mid-, and late (n = 3-6/stage) follicular and luteal phases of the cycle. The tissues were processed for indirect immunocytochemical localization of receptors with specific monoclonal antibodies against ER (H222 and D75) and PR (JZB39). Specific immunocytochemical staining, as determined by comparing adjacent tissue sections incubated with either receptor antibodies or a nonspecific antibody, was exclusively nuclear. Both ER and PR were localized in the germinal epithelium of ovaries at all stages of the cycle. ER was not detected in any other ovarian structure (i.e. stroma, follicles, interstitial tissue, or copora lutea) regardless of the stage of development. However, ER was detected in other estrogen-responsive tissues, e.g. the oviduct of the monkey and copora lutea of the pseudopregnant rabbit. In the monkey ovary, PR was detected in stromal and interstitial tissues as well as theca interna and externa of healthy and atretic follicles at all stages of the cycle. The granulosa cells of some primordial and primary follicles demonstrated staining for PR. However, the granulosa layer of follicles that developed beyond the primary stage were consistently negative for PR. Only the granulosa layer of large preovulatory follicles that showed signs of luteinization after the LH surge showed staining for PR equivalent to that in the theca. Monkey corpora lutea exhibited specific nuclear staining for PR. Moreover, the percentage of receptorpositive nuclei in the corpus luteum varied (P < 0.05) between the early (28 .+-. 3%), mid (48 .+-. 1%)-, and late (4 .+-. 2%) luteal phase of the cycle. Nonfunctional (serum progesterone < 0.5 ng/ml) regressing copora lutea did not exhibit for staining for PR. Luteal cells that were PR positive also contained histochemically detectable 3.beta.-hydroxysteroid dehydrogenase. These data are consistent with the concept of a receptor-mediated autocrine or paracrine role for progestins, but not estrogens in the gametogenic and endocrine functions of the primate ovary throughout the menstrual cycle.