Immunohistochemical localization of 17 alpha-hydroxylase/C17-20 lyase and aromatase cytochrome P-450 in the human ovary during the menstrual cycle.

Immunohistochemical localization of 17 alpha-hydroxylase/C17-20 lyase (P-450(17 alpha,lyase)) and aromatase cytochrome P-450 (P-450arom) in normal human ovaries during the menstrual cycle was studied using specific polyclonal antibodies which were raised against corresponding enzymes. In the follicular phase of matured follicles, P-450(17 alpha,lyase) was localized in theca interna cells and P-450arom in granulosa cells. P-450(17 alpha,lyase) was expressed in theca interna cells before P-450arom was expressed in granulosa cells. The corpus luteum showed immunoreactivity to both enzymes and, after menstruation, immunoreactivity decreased gradually until it could not be detected in the corpus albicans. In corpus luteum graviditatis the immunoreactivity continued to be expressed strongly. In some atretic follicles, P-450(17 alpha,lyase) and/or P-450arom continued to be expressed. In the stromal layer, P-450(17 alpha,lyase was detected in secondary interstitial cells, which originated from the theca interna of atretic follicles, and P-450arom was detected in hilar cells. Immunoreactivity to both enzymes was also detected in oocytes of developing follicles. These results are consistent with the two cell theory in the human ovary. They also suggest that androgens and oestrogens are produced not only by follicles and corpora lutea but also by stroma and oocytes.