Gonadotropic control of secretion of dimeric inhibins and activin A by human granulosa-luteal cells in vitro

Purpose: It is well established that human granulosa cells and luteal cells express inhibin/activin subunit protein and secrete immunoreactive inhibin. The gonadotropic control of secretion of different molecular forms of inhibin and activin A by granulosa-luteal cells (G-LCs) was investigated using recently developed specific enzyme immunoassays (ELAs). Methods: Granulosa-luteal cells obtained at IVF egg pickup were cultured in a serum-free medium at 37 degrees C in a water-saturated incubator with 5% CO2 for up to 5 days. Experiments with varying concentrations of human FSH, hLH, and hCG were carried out. Results: FSH raised the secretion of inhibin A and pro-alpha C-containing inhibins after 24 and 48 hr in culture, inhibin B was raised after 24 hr and activin A was raised after 48 hr of FSH treatment. LH treatment for 24 hr stimulated inhibin A, inhibin B, pro-alpha C, and activin A. hCG stimulated G-LC secretion of inhibin A after 48 hr mid pro-alpha C after 24 hr Paradoxically, inhibin B secretion was inhibited by 1 and 10 ng/ml hCG after 48 hr Activin A was stimulated by hCG after 24 and 48 hr of incubation. G-LC secretion of estradiol and progesterone was also stimulated significantly by LH and hCG. Conclusions: Secretion of dimeric inhibins and activin A is controlled differentially by gonadotropins.