IDENTIFICATION AND SYNTHETIC PATHWAY OF THE MATURATION-INDUCING HORMONE IN THE MARINE TELEOST

本研究对河豚、黄尾、赤鲷、鲭鱼和竹叶濑鱼等5种海洋硬骨鱼的卵黄发生和卵母细胞成熟过程中的类固醇合成途径进行了研究，发现在河豚、黄尾和鲭鱼的卵黄发生卵泡中，E2由雄烯二酮（AD）经睾酮（T）合成，而在红海蜇和竹叶隆头鱼中，E_2是由AD经雌酮（E_1）合成的，而在T.在FOM期间，在所有物种中，发生了从雌二醇-17 β到20β-羟基化的孕酮生成的类固醇生成转变。在所产生的甾体中，17，20 β-二羟基-4-异戊烯-3-酮（17，20 β-P）和17，20 β，21-三羟基-4-异戊烯-3-酮（20β-S）在所有物种的体外对生殖囊泡破裂（GVBD）表现出最大的影响。17，20 β-二羟基-4-异戊烯-3-酮（17，20 β-P）是黄尾鱼的一种成熟诱导激素。在河豚鱼中发现17，20 β，21-三羟基-4-异戊烯-3-酮（20β-S）是河豚鱼的MIH。另一方面，在日本鲭鱼、赤鲷和竹叶隆头鱼中，已经阐明17，20 β-P和20β-S都起着MIH的作用。此外，本研究阐明了每个物种中MIH的合成途径。在所有情况下，卵泡中C17，20-裂解酶的失活和20β-羟基类固醇脱氢酶的激活的组合是FOM中常见的酶动力学。

In this research project, steroid synthetic pathways in the ovarian follicles of the five species of marine teleost, tiger puffer, yellow tail, red seabream, Japanese mackerel, and bambooleaf wrasse, during vitellogenesis and final oocyte maturation (FOM) were investigated.In the vitellogenic ovarian follicles in the tiger puffer, yellowtail, and Japanese mackerel, E2 is synthesized from androstendione (AD) via testosterone (T), while in red seabream and bambooleaf wrasse E2 is synthesized from AD via estrone (E1) but not T. During FOM, in all species the steroidogenic shift from estradiol-17β to 20β-hydroxylated progestin production occurred. Of the steroids produced, 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) and 17,20β,21-trihydroxy-4-pregnen-3-one (20β-S) exhibited the greatest effect on germinal vesicle breakdown (GVBD) in vitro in all species. 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) is confirmed as a maturation-inducing hormone (MIH) of the yellowtail. In the tiger puffer, it was shown that 17,20β,21-trihydroxy-4-pregnen-3-one (20β-S) was the MIH of this species. On the other hand, in the Japanese mackerel, red seabream, and bamboleaf wrasse, it has been clarified that both 17,20β-P and 20β-S play a role as MIH. Furthermore, the present study clarified the synthetic pathway of the MIH (s) in each species. In all cases, a combination of inactivation of C17, 20-lyase and activation of 20β-hydroxysteroid dehydrogenase in the ovarian follicles is the common enzymatic kinetics in the FOM.