Study of action mechanism of gonad-stimulating hormone (GSS) in starfish

与脊椎动物相似，海星卵母细胞减数分裂的恢复是由激素作用控制的。此前，作为促性腺激素的性腺刺激物质(GSS)是从海星(Asterina Pectinifera)中纯化出来的，随后，它的结构被破译。在这里，我们展示了GSS对海星卵母细胞成熟的激素作用。根据生物活性，GSS主要分布于放射神经和神经环。在胃部和管足中也含有微量的生殖素，但在卵巢和睾丸中检测不到。此外，在动物产卵前后的体腔液中检测到生殖素活性，也证实了GSS作用于卵巢产生第二介体1-甲基腺嘌呤(1-Meade)，这是海星的成熟诱导激素。1-Meade是由卵母细胞周围的卵泡细胞在GSS刺激下产生的。合成的生殖素通过环磷酸腺苷(CAMP)的产生刺激成熟卵巢的卵泡细胞产生1-甲基-天冬氨酸(1-Mead)。然而，在生殖器存在的生长期，卵泡细胞中既没有产生1-Meade，也没有产生cAMP。用放射性碘标记和放射性惰性生殖素作卵泡细胞的竞争性实验，成熟期的Kd值低于生长期，但两者的Bmax值相近。似乎在繁殖季节之后，卵泡细胞中生殖素受体的亲和力变得足够高，足以激活G蛋白和腺苷环化酶。这些发现表明，产卵时，从神经系统分泌到体腔液的生殖素作用于卵泡细胞产生1-甲基-天冬氨酸，从而诱导卵母细胞成熟。

Similar to that in vertebrates, resumption of meiosis in starfish oocytes is controlled by hormonal action. Previously, the gonad-stimulating substance (GSS) that acts as gonadotropin was purified from the starfish (Asterina pectinifera) and subsequently, its structure was deciphered. Here, we show that hormonal action of GSS on oocyte maturation of starfish A. pectinifera. Based on biological activity, GSS was principally distributed to radial nerves and nerve rings. A trace amount of genitalin was also contained in cardiac stomach and tube-feet, but it was undetectable in the ovaries and testes. Furthermore, the genitalin activity was detectable in coelomic fluid of animals during spawning, though there was no detectable activity in the fluid from animals before or after spawning.It has also been demonstrated that GSS acts on the ovary to produce the second mediator 1-methyladenine (1-MeAde) which is the maturation-inducing hormone of starfish. 1-MeAde is produced by ovarian follicle cells around oocytes upon stimulation with GSS. The synthetic genitalin stimulated follicle cells in ripe ovaries to produce 1-MeAde through arise in cyclic AMP (cAMP). However, neither 1-MeAde nor cAMP production occurred in follicle cells during the growing stage in the presence of genitalia. According to competitive experiments using radioiodinated and radioinert genitalin in follicle cells, the Kd value in the ripe stage was lower than that in the growing stage, although similar Bmax values were obtained in both stages. It seems that the affinity of receptors for genitalin in ovarian follicle cells becomes high enough to activate G-proteins and adenylyl cyclase following the breeding season. These findings suggest that, upon spawning, the genitalin secreted from nervous system to the coelomic fluid acts on 1-MeAde production by follicle cells to induce oocyte maturation.