Follicle-Stimulating Hormone Induction of Luteinizing Hormone Receptor in Cultured Rat Granulosa Cells: An Examination of the Need for Steroids in the Induction Process*

Abstract

The induction of LH receptors by FSH in cultured rat granulosa cells and the effects of ovarian steroids on this process were examined. Granulosa cells were isolated from the ovaries of untreated immature rats (25 days old) and cultured with highly purified FSH (Sairam; 250 ng/ml). After culture (48-96 h in chemically defined media), both the binding of [125I]hCG and the responsiveness (cAMP and progesterone production) to an acute LH stimulus (100 ng/ml; NIH B8) were measured. The appearance of LH/hCG-binding sites and LH responsiveness indicates the presence of functional LH receptors. The induction of LH receptors by FSH requires a lag period of 24-48 h. After 48 h, the concentration of LH receptors in cultured granulosa cells continues to increase with time in culture with FSH; the continuous presence of FSH is required to maintain the induction process. If granulosa cells are cultured without hormone for 24-48 h before FSH is added, no induction of LH receptors occurs. However, if 17 beta-estradiol (5 X 10(-7) M) is added during this initial period, then the cells are responsive to the later addition of FSH. This maintenance of FSH responsiveness is not observed when dihydrotestosterone or progesterone is substituted for 17 beta-estradiol in the initial culture period. The FSH-dependent induction of LH receptors in cultured rat granulosa cells can be blocked if an inhibitor of steroidogenesis, such as aminoglutethimide phosphate (AGP; 1 mM), is added along with FSH at the initiation of the culture. The inclusion of progesterone, dihydrotestosterone, or 17 beta-estradiol (but not 20 alpha-dihydroprogesterone) in the culture together with FSH and AGP will overcome the inhibition by AGP and restore the induction of LH receptors. The results suggest that steroids produced by the developing follicle can modulate the FSH-dependent induction of LH receptors, and this may play a role in the development of follicular responsiveness to LH.

Homologous Regulation of Hormone Receptors: Luteinizing Hormone Increases Its Own Receptors in Cultured Rat Granulosa Cells*

“…Similar to an earlier study suggesting that the continuous presence of FSH is necessary for LH receptor maintenance (10), the present studies indicate that LH is also capable of enhancing LH receptors in FSH-primed granulosa cells in vitro. Time-course studies indicate that the LH receptor content is increased within 12 h of initiation of LH treatment.…”

“…2. Consistent with previous observations (9)(10)(11), FSH treatment produced a dose-dependent increase in LH receptor content ( Fig. 2A, ) compared to that of FSH-primed cells without further hormone exposure.…”

“…While granulosa cells acquire FSH receptors during early stages of follicular development (1,3), LH receptors only appear on granulosa cells during late stages of follicular growth (4)(5)(6). Several groups demonstrated that FSH induces LH receptors in rat granulosa cells in vivo (4,7,8) and in vitro (9)(10)(11), while PRL maintains LH receptors in these cells (12,13).…”

Luteinizing hormone receptor appearance in cultured porcine granulosa cells requires continual presence of follicle-stimulating hormone.

“…A possible role for progesterone as a mediator of FSH induction of LH receptors has been suggested previously (5). Therefore, to examine directly whether progesterone is involved in the induction process of LH receptors by FSH, we studied the effect of aminoglutethimide on FSH-mediated LH receptor induction.…”

“…1 for review). In recent years, several different systems have been described in which primary cultures of granulosa cells are maintained such that they retain their ability to respond in vitro to FSH with an increase in the density of LH receptors (2)(3)(4)(5)(6). It has been shown that the ability of FSH to induce LH receptors in granulosa cells is due to its ability to activate adenylate cyclase because other compounds that stimulate adenylate cyclase, such as cholera toxin, or the direct addition of cAMP or its analogues to the cells also cause the appearance of LH receptors (4,(7)(8)(9)).…”