Ge W, Peter R E
Department of Zoology, University of Alberta, Edmonton, Canada.
Gen Comp Endocrinol. 1994 Aug;95(2):213-21. doi: 10.1006/gcen.1994.1118.
Activin and inhibin, dimeric protein hormones originally isolated from mammalian gonads, are involved in the regulation of pituitary gonadotropin secretion. Using domain-specific antibodies against activin and inhibin alpha, beta A, and beta B subunits, the present study demonstrates that immunoreactive activin and inhibin subunits, especially beta A, exist in goldfish pituitary. Immunocytochemical staining with anti-gonadotropin-II and anti-growth hormone showed that the pituitary cells containing immunoreactive activin beta subunits are somatotrophs. This is different from the situation in mammals where it is the gonadotrophs that produce activin molecules within the pituitary. The staining with anti-beta B was overall weak compared to that with anti-beta A, but both appear to localize in the same cells. Strong immunostaining with the anti-inhibin alpha subunit was also observed in the goldfish pituitary; however, the immunoreactivity is dissociated from those of beta A and beta B, and mainly associated with nerve fibers in the neurointermediate lobe. Based on this evidence, it is suggested that the goldfish pituitary predominantly produced activin-like molecules. Both porcine activin and inhibin stimulate growth hormone release from perifused goldfish pituitary fragments. Taken together with our previous findings that porcine activin stimulates gonadotropin-II release in goldfish, and the fact that the somatotrophs and gonadotrophs are in close contact with each other in the goldfish pituitary, it is hypothesized that somatotroph-derived activin may exert paracrine actions on the adjacent gonadotrophs to stimulate gonadotropin release and autocrine actions on somatotrophs to stimulate growth hormone secretion. This also provides a mechanism for communication between these two pituitary cell types.
激活素和抑制素是最初从哺乳动物性腺中分离出来的二聚体蛋白激素，参与垂体促性腺激素分泌的调节。本研究使用针对激活素和抑制素α、βA和βB亚基的结构域特异性抗体，证明金鱼垂体中存在免疫反应性激活素和抑制素亚基，尤其是βA。用抗促性腺激素-II和抗生长激素进行免疫细胞化学染色显示，含有免疫反应性激活素β亚基的垂体细胞是生长激素细胞。这与哺乳动物的情况不同，在哺乳动物中，是促性腺激素细胞在垂体内产生激活素分子。与抗βA染色相比，抗βB染色总体较弱，但两者似乎都定位在相同的细胞中。在金鱼垂体中也观察到抗抑制素α亚基的强免疫染色；然而，其免疫反应性与βA和βB的免疫反应性分离，主要与神经中间叶的神经纤维相关。基于这些证据，提示金鱼垂体主要产生激活素样分子。猪激活素和抑制素均刺激从灌注的金鱼垂体片段释放生长激素。结合我们之前的发现，即猪激活素刺激金鱼促性腺激素-II释放，以及金鱼垂体中生长激素细胞和促性腺激素细胞彼此紧密接触这一事实，推测生长激素细胞来源的激活素可能对相邻的促性腺激素细胞发挥旁分泌作用以刺激促性腺激素释放，对生长激素细胞发挥自分泌作用以刺激生长激素分泌。这也为这两种垂体细胞类型之间的通讯提供了一种机制。
