Use of antisera to follicle-stimulating hormone (FSH) to detect non-FSH factors in human serum which modulate rat granulosa cell steroidogenesis.

We measured the ability of serum from women to stimulate steroidogenesis in cultured granulosa cells. Serum promoted estradiol and progesterone synthesis in proportion to its FHS content measured by RIA [i.e. serum from postmenopausal women (PM) greater than serum from the midcycle at the time of the gonadotropin surge (MC) greater than serum from the first day of the menstrual cycle (D1) greater than serum from a hypophysectomized woman (AP)]. The FSH activity of these sera was reduced but not eliminated when we included excess antisera to ovine or human FSH in the culture medium (i.e. PM greater than MC greater than D1 greater than AP). These antisera completely neutralized the actions of ovine FSH, human FSH, and menopausal gonadotropin (Pergonal) added to serum. In contrast to the stimulation seen with 5% or lower concentrations of serum in the culture medium, we observed that 10-20% serum inhibited FSH-induced androgen aromatization and progesterone accumulation. The degree of stimulation or inhibition of steroidogenesis depended on the number of granulosa cells added to each culture. High initial cell concentrations inhibited the ability of the cells to respond to either serum or PMSG. In addition to factors which stimulate or inhibit FSH-induced steroidogenesis, human serum contains factors distinct from FSH which cause the cells to flatten and adhere more tightly to the culture dishes. Although progesterone synthesis was increased in cells which had flattened on the surface of the culture dishes, this phenomenon was not a prerequisite for serum-induced steroidogenesis. We conclude that serum contains factors immunologically distinct from FSH, possibly of pituitary origin, which induce granulosa cell steroidogenesis. In addition, serum contains inhibitory substances which block hormone-induced steroidogenesis and which tend to obscure the stimulatory effects of FSH. Detection of both factors depends in part on the number of granulosa cells used to innoculate the cell cultures.