The Robert H. Smith Faculty of Agriculture, Food and Environment, Department of Animal Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
Gen Comp Endocrinol. 2010 Feb 1;165(3):412-37. doi: 10.1016/j.ygcen.2009.07.019. Epub 2009 Aug 15.
Teleosts lack a hypophyseal portal system and hence neurohormones are carried by nerve fibers from the preoptic region to the pituitary. The various cell types in the teleost pituitary are organized in discrete domains. Fish possess two gonadotropins (GtH) similar to FSH and LH in other vertebrates; they are heterodimeric hormones that consist of a common alpha subunit non-covalently associated with a hormone-specific beta subunit. In recent years the availability of molecular cloning techniques allowed the isolation of the genes coding for the GtH subunits in 56 fish species representing at least 14 teleost orders. Advanced molecular engineering provides the technology to produce recombinant GtHs from isolated cDNAs. Various expression systems have been used for the production of recombinant proteins. Recombinant fish GtHs were produced for carp, seabream, channel and African catfish, goldfish, eel, tilapia, zebrafish, Manchurian trout and Orange-spotted grouper. The hypothalamus in fishes exerts its regulation on the release of the GtHs via several neurohormones such as GnRH, dopamine, GABA, PACAP, IGF-I, norepinephrine, NPY, kisspeptin, leptin and ghrelin. In addition, gonadal steroids and peptides exert their effects on the gonadotropins either directly or via the hypothalamus. All these are discussed in detail in this review. In mammals, the biological activities of FSH and LH are directed to different gonadal target cells through the cell-specific expression of the FSH receptor (FSHR) and LH receptor (LHR), respectively, and the interaction between each gonadotropin-receptor couple is highly selective. In contrast, the bioactivity of fish gonadotropins seems to be less specific as a result of promiscuous hormone-receptor interactions, while FSHR expression in Leydig cells explains the strong steroidogenic activity of FSH in certain fish species.
硬骨鱼类缺乏垂体门脉系统，因此神经激素通过来自前脑区域的神经纤维传递到垂体。硬骨鱼类垂体中的各种细胞类型组织在离散的区域中。鱼类具有两种类似于其他脊椎动物中的 FSH 和 LH 的促性腺激素（GtH）；它们是异二聚激素，由非共价结合的共同α亚基与激素特异性β亚基组成。近年来，分子克隆技术的可用性允许从代表至少 14 个硬骨鱼目 56 种鱼类中分离出编码 GtH 亚基的基因。先进的分子工程提供了从分离的 cDNA 生产重组 GtH 的技术。已经使用各种表达系统生产重组蛋白。已经生产了用于鲤鱼、真鲷、鲤鱼和非洲鲶鱼、金鱼、鳗鱼、罗非鱼、斑马鱼、鳜鱼和橙色斑点石斑鱼的重组鱼 GtH。鱼类的下丘脑通过几种神经激素（如 GnRH、多巴胺、GABA、PACAP、IGF-I、去甲肾上腺素、NPY、kisspeptin、瘦素和 ghrelin）对 GtH 的释放发挥其调节作用。此外，性腺类固醇和肽通过下丘脑或直接作用于促性腺激素发挥其作用。本文详细讨论了所有这些内容。在哺乳动物中，FSH 和 LH 的生物学活性通过 FSH 受体（FSHR）和 LH 受体（LHR）的细胞特异性表达分别针对不同的性腺靶细胞，并且每种促性腺激素-受体对的相互作用具有高度选择性。相比之下，由于激素-受体相互作用的混杂，鱼类促性腺激素的生物活性似乎不那么特异，而 FSHR 在 Leydig 细胞中的表达解释了 FSH 在某些鱼类物种中的强烈类固醇生成活性。
