Functional and structural relationships in steroidogenesis in vitro by human ovarian follicles during maturation and ovulation.

To investigate steroidogenic function of human follicles in the light of their structures, eight antral follicles of different sizes were mechanically isolated from ovaries of patients laparotomized in the follicular phase of the menstrual cycle with or without pretreatment with human menopausal gonadotropin (hMG). A portion of each follicle was taken for histology and slices of each follicle were incubated with [1-14C]-acetate. Incorporation into progestins, androgens, and estrogens was assessed by the reverse dilution technique with recrystallization to constant specific activity. A predominant incorporation into 17 beta-estradiol was observed in two maturing follicles, whereas a marked increase in incorporation into 17 beta-estradiol with a concomitant decrease in incorporation into androstenedione was verified in two other mature follicles. Remarkable enhancement in relative incorporation into C21 steroids was commonly noted in four preovulatory follicles. However, with the progress of preovulatory stages toward ovulation, as judged from structural changes of the follicles, actual incorporation into C19 and C18 steroids showed a moderate increase, followed by a drastic decrease around the time of ovulation. hMG injection induced similar relationships between the steroidogenic pattern and the follicle structure of different stages, although overall incorporation was considerably increased. We conclude that marked qualitative and quantitative changes in the steroidogenic function and accompanying corresponding changes in structure occurred over the period of follicular maturation and ovulation.