Miró F, Smyth C D, Hillier S G
Department of Obstetrics and Gynaecology, University of Edinburgh, Scotland.
Endocrinology. 1991 Dec;129(6):3388-94. doi: 10.1210/endo-129-6-3388.
Activin is structurally related to polypeptide growth factors such as transforming-growth factor-beta, which may have paracrine and/or autocrine functions in the ovaries. We have investigated the action of activin on granulosa cell steroidogenesis in vitro in relation to preovulatory follicular development in vivo. Estrogen-primed immature female rats received no other treatment (nondifferentiated granulosa cells), treatment with ovine (o) FSH (differentiated granulosa cells), or treatment with oFSH followed by human (h) CG (preovulatory granulosa cells) to stimulate preovulatory follicular development. Granulosa cells were isolated and cultured in the presence and absence of recombinant human activin-A using serum-free medium supplemented with 1.0 microM testosterone as an aromatase substrate and hFSH, hLH, forskolin, or 8-bromo-cAMP to stimulate steroid synthesis in vitro. After 48 h, medium was collected for measurement of estradiol (aromatase activity), progesterone, and cAMP. Basal steroid synthesis in nondifferentiated granulosa cells was unaffected by activin, but both aromatase activity and progesterone production induced by treatment with FSH in vitro were dosedependently enhanced up to 10-fold by the presence of activin. FSH-stimulated cAMP production was not measurably altered by activin; however, steroidogenesis induced by forskolin or 8-bromo-cAMP was significantly enhanced by the factor. Thus the effect of activin on steroidogenesis includes action at a subcellular level(s) distal to the production of cAMP. After gonadotropin treatment in vivo, granulosa cell aromatase activity and progesterone production showed divergent responses to activin in vitro. Basal-, FSH-, and LH-stimulated aromatase activity were all enhanced by activin in cultures of differentiated and preovulatory granulosa cells. However, whereas basal progesterone production was stimulated by activin in cultures of differentiated granulosa cells, in preovulatory granulosa cells it was inhibited. Moreover, in vitro stimulation of progesterone production by treatment of both differentiated and preovulatory granulosa cells with FSH or LH was suppressed by the presence of activin. Thus rat granulosa cells display development-related steroidogenic responses to activin, aromatase production becoming enhanced and progesterone production suppressed as follicular maturation progresses. These results further implicate activin as a local modulator of granulosa cell steroid synthesis in the ovaries, although its functional significance has yet to be established.
激活素在结构上与诸如转化生长因子-β等多肽生长因子相关，后者在卵巢中可能具有旁分泌和/或自分泌功能。我们已经研究了激活素在体外对颗粒细胞类固醇生成的作用，以及其与体内排卵前卵泡发育的关系。用雌激素预处理的未成熟雌性大鼠分别接受以下处理：不进行其他处理（未分化的颗粒细胞）、用羊（o）促卵泡激素（FSH）处理（分化的颗粒细胞）或先用oFSH处理，随后用人（h）绒毛膜促性腺激素（CG）处理（排卵前颗粒细胞），以刺激排卵前卵泡发育。分离颗粒细胞，并在添加1.0微摩尔睾酮作为芳香化酶底物以及hFSH、hLH、福斯可林或8-溴环磷酸腺苷（8-bromo-cAMP）以在体外刺激类固醇合成的无血清培养基中，分别在有和无重组人激活素-A的情况下进行培养。48小时后，收集培养基用于测定雌二醇（芳香化酶活性）、孕酮和环磷酸腺苷（cAMP）。未分化颗粒细胞的基础类固醇合成不受激活素影响，但在体外，激活素的存在使FSH处理诱导的芳香化酶活性和孕酮生成呈剂量依赖性增强，最高可达10倍。激活素对FSH刺激的cAMP生成无明显影响；然而，该因子显著增强了福斯可林或8-溴环磷酸腺苷诱导的类固醇生成。因此，激活素对类固醇生成的作用包括在cAMP产生的下游亚细胞水平发挥作用。在体内促性腺激素处理后，颗粒细胞芳香化酶活性和孕酮生成在体外对激活素表现出不同的反应。在分化的和排卵前颗粒细胞培养物中，基础、FSH和LH刺激的芳香化酶活性均被激活素增强。然而，在分化的颗粒细胞培养物中，基础孕酮生成受到激活素刺激，而在排卵前颗粒细胞中则受到抑制。此外，在分化的和排卵前颗粒细胞培养物中，FSH或LH处理对孕酮生成的体外刺激被激活素的存在所抑制。因此，大鼠颗粒细胞对激活素表现出与发育相关的类固醇生成反应，随着卵泡成熟的进展，芳香化酶生成增加而孕酮生成受到抑制。这些结果进一步表明激活素是卵巢中颗粒细胞类固醇合成的局部调节因子，尽管其功能意义尚待确定。
