Dynamic response to follicle-stimulating hormone of secretion of progesterone by superfused rat ovarian granulosa cells

Granulosa cells from immature female rats, pretreated with pregnant mare's serum gonadotropin, were cultured with microcarrier beads for 24 h, and superfused with culture medium. Progesterone was transiently released following a 10-min pulse of FSH (100 ng/ml), and there was a self-priming effect of FSH. 10-min pulses of 8-bromo-adenosine 3',5'-cyclic monophosphate (8Br-cAMP) (1 mg/ml) mimicked the effects of follicle-stimulating hormone (FSH). Continuous superfusion with FSH induced biphasic secretion of progesterone, which was composed of a parabolic (the first) and a plateau (the second) phase. By contrast, the pattern of secretion induced by continuous superfusion with 8Br-cAMP was monophasic. FSH-stimulated secretion of progesterone was rapidly inhibited by the addition of 10 microM cycloheximide (CX), but secretion recovered upon removal of this inhibitor. In the second phase, the recovery of secretion was accompanied by an overshoot of the plateau value. The present results suggest that: (1) the generation of the time-related biphasic pattern of secretion cannot be interpreted by cAMP alone; (2) FSH stimulates the secretion of progesterone by a mechanism that involves newly synthesized protein.