MODULATION OF THE EFFECTS OF FSH, ANDROSTENEDIONE, EPIDERMAL GROWTH-FACTOR (EGF) AND INSULIN-LIKE GROWTH-FACTOR-I (IGF-I) ON BOVINE GRANULOSA-CELLS BY GCIF, A GROWTH-INHIBITORY FACTOR OF LOW-MOLECULAR-MASS FROM BOVINE FOLLICULAR-FLUID

A granulosa cell-inhibitory factor (GCIF) of low molecular mass from b ovine follicular fluid inhibits the proliferation of bovine granulosa cells in vitro and the growth of large follicles in rats in vivo. The present study examined the ability of GCIF to modulate the effects of FSH, epidermal growth factor (EGF), insulin-like growth factor I(IGF-I ) and androstenedione on the proliferation of bovine granulosa cells a nd on aromatase activity in vitro. Granulosa cell proliferation was as sayed by counting haemocytometric cells and by measuring the incorpora tion of [H-3]thymidine into acid-precipitable material. Assay of aroma tase activity was based on the conversion of [H-3]androstenedione to [ H-3]H2O. FSH, androstenedione, EGF and IGF-I all stimulated (P < 0.01) granulosa cell proliferation; however, the addition of GCIF reduced ( P < 0.01) cell proliferation in their presence. In the case of EGF, th e addition of GCIF almost abolished the stimulatory response. FSH and IGF-I, but not EGF, stimulated (P < 0.01) aromatase activity of granul osa cells. The stimulatory effect of IGF-I was decreased by GCIF. The inhibitory effects of GCIF indicate that it may play a significant rol e in regulating the effects of intraovarian growth factors on granulos a cells and the growth of follicles.