Yuen Chi-Wai, Ge Wei
Department of Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
Gen Comp Endocrinol. 2004 Jan 1;135(1):108-15. doi: 10.1016/j.ygcen.2003.08.012.
Our previous study demonstrated that recombinant goldfish activin B stimulated goldfish FSHbeta but inhibited LHbeta expression. Similar to activin B, activin A also exhibited the inverse effects on the expression of the two gonadotropins. The novel dual effects of activins on FSH and LH in the goldfish raise an interesting question as to where the activin comes from in vivo. In the present study, we first demonstrated the expression of activin, its receptors and binding protein follistatin in the goldfish pituitary, leading to a suggestion that an autocrine/paracrine regulatory system involving activin is operative in fish pituitary. To investigate the functionality of the pituitary-derived activin system in the regulation of gonadotropin biosynthesis, we further examined the effects of follistatin, an activin-binding protein, on goldfish FSHbeta and LHbeta expression. Follistatin not only reversed the effects of exogenous activin on FSHbeta and LHbeta expression but also had inverse effects on the basal expression of the genes; and its effects were opposite to those of activin. This suggests that the endogenous activin plays roles in controlling the expression of both FSHbeta and LHbeta genes. It is conceivable that any factors that influence the intrapituitary activin system in vivo will likely affect the biosynthesis of the two gonadotropins in the goldfish.
我们之前的研究表明，重组金鱼激活素B可刺激金鱼促卵泡激素β（FSHβ）的表达，但抑制促黄体激素β（LHβ）的表达。与激活素B类似，激活素A对这两种促性腺激素的表达也表现出相反的作用。激活素对金鱼FSH和LH的这种新型双重作用引发了一个有趣的问题，即激活素在体内的来源。在本研究中，我们首先证明了激活素及其受体和结合蛋白卵泡抑素在金鱼垂体中的表达，这表明涉及激活素的自分泌/旁分泌调节系统在鱼类垂体中起作用。为了研究垂体来源的激活素系统在促性腺激素生物合成调节中的功能，我们进一步研究了激活素结合蛋白卵泡抑素对金鱼FSHβ和LHβ表达的影响。卵泡抑素不仅逆转了外源性激活素对FSHβ和LHβ表达的影响，而且对这些基因的基础表达也有相反的作用；其作用与激活素相反。这表明内源性激活素在控制FSHβ和LHβ基因的表达中起作用。可以想象，体内任何影响垂体激活素系统的因素都可能影响金鱼中这两种促性腺激素的生物合成。
