In situ hybridization study of messenger RNA for estrogen receptor and immunohistochemical detection of estrogen and progesterone receptors in the human ovary

The expression of estrogen and progesterone receptors (ER and PR), as well as the presence of messenger RNA for estrogen receptor (ER-mRNA), were analyzed by immunohistochemistry and in situ hybridization, respectively, in the ovary of 25 healthy eumenorrheic women. Ovarian biopsies were taken in different phases of the menstrual cycle during laparotomy or operative laparoscopy performed for extraovarian benign diseases. A total of 126 follicles (105 primordial, 13 preantral and eight antral) and 50 corpora lutea (eight active and 42 atretic) was analyzed. Granulosa cells stained positively for ER, PR and ER-mRNA in 13.3, 9.5 and 17.1% of primordial follicles, respectively. The proportions of preantral and antral follicles with ER-positive granulosa cells were 23.1 and 37.5%, respectively; these follicles were positive for PR in 23.1 and 37.5% of cases, and for ER-mRNA in 30.7 and 37.5% of cases, respectively. For thecal cells, 38.5% of preantral and 37.5% of antral follicles were PR-positive, but no more than 25% stained positive for ER and ER-mRNA. Active corpora lutea stained positive for ER, PR and ER-mRNA in 50, 62.5 and 50% of cases, respectively. Corpora albicantes always stained negative. In all subjects the stroma surrounding both follicles and corpora lutea contained several fibroblast-like cells which stained positive for ER, PR and ER-mRNA. Oocytes and blood vessels stained negative in all cases. This study supports the hypothesis that estrogens and progesterone play a role in the intraovarian regulation of follicle growth from the first steps of follicle development, and participate in the regulation of corpus luteum.