BASIC FIBROBLAST GROWTH-FACTOR INDUCES LUTEINIZING-HORMONE RECEPTOR EXPRESSION IN THE PRESENCE OF INSULIN-LIKE GROWTH-FACTOR-I IN OVARIAN GRANULOSA-CELLS

Effect of basic fibroblast growth factor (bFGF) on the expression of r eceptors for luteinizing hormone (LH), a marker of differentiation, wa s studied using estrogen-primed rat ovarian granulosa cells in primary culture. bFGF had no effect by itself but dose-dependently induced ex pression of functional LH receptors in the presence of insulin-like gr owth factor-I (IGF-I). The effect of a combination of bFGF and IGF-I w as delayed in onset and the magnitude of the response was smaller when compared to the action of follicle-stimulating hormone (FSH). Scatcha rd analysis revealed that dissociation constant (K-d) and number of LH receptors induced by bFGF and IGF-I were 0.47 nM and 6.48 fmol/10(6) cells, respectively. Unlike FSH, bFGF plus IGF-I did not cause an imme diate increase in cAMP release, however, considerable amount of cAMP r elease was observed in cells incubated for 72 h with bFGF plus IGF-I. Indomethacin, an inhibitor of cyclooxygenase, attenuated both LH recep tor expression and cAMP release induced by bFGF plus IGF-I but had lit tle effect on the action of FSH. Finally, a combination of bFGF and IG F-I increased production of prostaglandin E(2) in granulosa cells. The se results indicate that bFGF is capable of inducing LH receptor in th e presence of IGF-I by a mechanism involving production of prostagland in E(2).