Progesterone receptor, but not estradiol receptor, messenger ribonucleic acid is expressed in luteinizing granulosa cells and the corpus luteum in rhesus monkeys

Estrogens (i.e. estradiol) and progestins (i.e. progesterone) may act as local regulators of ovarian function in various species. This study tested the hypothesis that if progesterone and estradiol act via receptor-mediated pathways in the primate ovary, then receptor messenger RNAs (mRNAs) should be detectable in ovarian cells. The reverse transcription-polymerase chain reaction (RT-PCR) was employed to detect progesterone and estradiol receptor (PR and ER, respectively) mRNAs in the rhesus monkey ovary. Total RNA was isolated from macaque uterine myometrium (positive control), spleen (negative control), whole ovary, germinal (surface) epithelium-enriched cortical and medullary compartments of the ovary, granulosa cells in preovulatory follicles before and after an ovulatory stimulus, and corpora lutea from early (days 3-5), mid (days 7 and 8)-, and late (days 14 and 15) luteal phase of the menstrual cycle. Using primers to the hormone-binding region encoded by the receptor mRNAs, RT-PCR products of the expected sizes were detected for PR and ER from 1 μg myometrial RNA, whereas products were not obtained from spleen. PR mRNA product was detected in all ovaries, germinal epithelium-enriched cortical and medullary compartments, and corpora lutea from all three stages of the luteal phase (n = 3/stage). PR mRNA product was detected as a strong hand in one of three preparations obtained from granulosa cells before an ovulatory stimulus. In contrast, PR mRNA was detected in granulosa cells from all animals after an ovulatory dose of hCG. ER mRNA was detected in whole ovary and in germinal epithelium-enriched cortical compartments, with a barely visible product occasionally observed in medullary compartments of the ovary. In contrast to PR mRNA, ER mRNA was not detected in any corpora lutea throughout the luteal phase or in granulosa cells obtained before or after an ovulatory stimulus. To confirm the specificity of the RT-PCR products, restriction enzymes cleaved the PR product from myometrium, germinal epithelium-enriched cortical compartment and corpus luteum into the predicted size fragments. Similarly, the ER product from the myometrium and the germinal epithelium-enriched compartment was cleaved into the expected size fragments. Sequence analysis of the PR and ER RT-PCR products revealed 99% homology to the complementary DNA for the hormone-binding region of human PR and ER, respectively. Thus, PR mRNA detection supports the hypothesis of progesterone action via classical receptor-mediated pathways in the luteinizing follicle and corpus luteum of the primate ovary. The apparent absence of ER mRNA in these ovarian compartments suggests a lesser, if any, role for estradiol.