ELSEVIER Molecular and Cellular Endocrinology lOl(1994) 95-99 Molecular and ca Mar ElldOUinologY Basic fibroblast growth factor induces luteinizing hormone receptor expression in the presence of insulin-like growth factor-I in ovarian granulosa cells Makoto Kanzaki a, Masa-aki Hattori a, Ryuya Horiuchi b, Itaru Kojima *la zyxwvutsrqponmlk a Cell Biology Research Unit, Institute of Endocrinology, Gunma University, Maebashi, Japan; b Department of Pharmacy, Gunma University School of Medicine, Maebashi 371, Japan (Received 12 September 1993; accepted 10 December 1993) Abstract Effect of basic fibroblast growth factor (bFGF) on the expression of receptors for luteinizing hormone (LH), a marker of differentiation, was studied using estrogen-primed rat ovarian granulosa cells in primary culture. bFGF had no effect by itself but dose-dependently induced expression of functional LH receptors in the presence of insulin-like growth factor-I (IGF-I). The effect of a combination of bFGF and IGF-I was delayed in onset and the magnitude of the response was smaller when compared to the action of follicle-stimulating hormone (FSH). Scatchard analysis revealed that dissQciation constant (K,) and number of LH receptors induced by bFGF and IGF-I were 0.47 nM and 6.48 fmol/106 cells, respedtively. Unlike FSH, bFGF plus IGF-I did not cause an immediate increase in CAMP release, however, considerable amount of CAMP release was observed in cells incubated for 72 h with bFGF plus IGF-I. Indomethacin, an inhibitor of cyclooxygenase, attenuated both LH receptor expression and CAMP release induced by bFGF plus IGF-I but had little effect on the action of FSH. Finally, a combination of bFGF and IGF-I increased production of prostaglandin E, in granulosa cells. These results indicate that bFGF is capable of inducing LH receptor in the presence of IGF-I by a mechanism involving production of prostaglandin E,. Key words: Fibroblast growth factor; Granulosa cell differentiation 1. Introduction Basic fibroblast growth factor (bFGF) augments cel- lular proliferation and differentiation in various types of cells in culture and also plays an important role in vivo in controlling proliferation, neovascularization and cellular differentiation (Folkman and Klagsbrun, 1987; Gospodarowicz et al., 1987; Rifkin and Moscatelli, 1989). bFGF is also known as heparin-binding growth factor-2 (Gospodarowicz et al., 1987) and heparin-like molecules in extracellular matrix are required for bind- ing of bFGF to the high-affinity receptor (Rapraeger et al., 1991; Yayon et al., 1991). bFGF, which was origi- nally identified in pituitary gland and brain (Gospo- darowicz, 19751, was also isolated from corpus luteum (Gospodarowicz et al., 1985). Several recent studies * Corresponding author. Tel.: 81-272-31-7221; Fax: 81-272-34-2026. Elsevier Science Ireland Ltd. SSDI 0303-7207(93)E0308-H suggest a possibility that bFGF affects cellular func- tions in granulosa cells as an autocrine/paracrine fac- tor (Gospodarowicz et al., 1977; La Polt et al., 1990; Neufeld et al., 1987; Shikone et al., 1992). Thus, bFGF stimulates growth of cultured granulosa cells (Gospo- darowicz and Ferrara, 19891, inhibits FSH-induced granulosa cell differentiation as judged by steroidogen- esis (Adashi et al., 1988; Baird and Hsueh, 1986) and expression of receptors for luteinizing hormone (LH) (Baird and Hsueh, 1986; Mondschein and Schomberg, 1981; Oury and Darbon, 1988; Piquette et al., 1991). Yet, the physiological implication of these observations is not totally certain and it is not known whether or not bFGF acts solely as an inhibitor of differentiation. In the present study, we evaluated the effect of bFGF on differentiation of rat ovarian granulosa cells in primary culture. The results indicate that bFGF is in fact capa- ble of inducing differentiation in the presehce of in- sulin-like growth factor-I (IGF-I).