BIOYSNTHESIS OF ESTROGEN AND ITS PHYSIOLOGICAL ROLE ON THE SPAWNING IN MARINE BIVALVES

(1)用高效液相色谱-电子捕获检测器检测到雌酮(E_1)、雌二醇-17β(E_2)和少量雌三醇(E_3)在卵巢的生殖周期及其生物合成中的分布，而在睾丸中只有E_2。卵巢中的E_2水平始终高于E_1，并且随性成熟而升高。这些结果表明，E_2可能在牡蛎和扇贝的生殖活动中起作用。体外实验证明，两种双壳贝类卵巢中均存在17β-羟基类固醇脱氢酶(17β-HSD)。产卵后卵巢中17β-HSD活性低于分化早期。用~3H-水试剂法证实了扇贝卵巢中存在芳香酶活性。3β-羟基类固醇脱氢酶(3β-HSD)、P450芳香酶和E_2在扇贝卵巢生殖管上皮细胞中呈阳性反应。结论：雌激素可以…(2)卵子发生过程中卵母细胞膜上5-羟色胺受体的形成5-羟色胺(5-羟色胺，5-羟色胺)是触发双壳类软体动物产卵的主要神经递质，主要是其生发泡破裂(GVBD)。本研究采用[~3H]5-羟色胺结合分析方法，对扇贝和牡蛎卵母细胞膜上可能存在的受体进行了研究，揭示了5-羟色胺受体在扇贝和牡蛎卵母细胞生长过程中的作用及其激素调控作用。扇贝和牡蛎卵母细胞表面5-羟色胺的解离常数分别为2.64和2.01微米，其最大结合容量扇贝和牡蛎分别为152和529微克/毫克蛋白。不同激动剂和拮抗剂对5-羟色胺的抑制作用提供了5-羟色胺受体在每个卵母细胞中的药理图谱：扇贝中5-HT1/5-HT2的混合图谱和牡蛎中相对单一的5-HT1图谱。17β雌二醇(E_2)可诱导扇贝卵母细胞表面5-羟色胺受体的形成，这可能是E_2促进5-羟色胺敏感性从而诱导产卵的主要原因。这种形成明显发生在E2调控下的卵母细胞生长过程中。较少

(1) Estrogen profile during the reproductive cycle and its biosynthesis in the ovaryEstrone (E1), estradiol-17beta (E2), and a small amount of estriol (E3) were identified in the ovary by HPLC-ECD,while only E2 was found in the testis. The level of E2 in the ovary was consistently higher than E1 and it increased with sexual maturation. These results indicate that E2 may play a role in the reproductive events of the oyster and scallop. In vitro experiments demonstrated the presence of 17beta-hydroxysteroid dehydrogenase (17beta-HSD) in the ovaries of both bivalves. The activity of 17beta-HSD in the ovary was lower in the post-spawning stage than in the early differentiating stage. The evidence for the presence of aromatase activity in the scallop ovary was obtained by 3H-water assay. The immunoreactivity against 3beta-hydroxysteroid dehydrogenase (3beta-HSD), P450 aromatase and E2 was detected in the cells along the genital tubule of the scallop ovary. It is concluded that estrogens can … More be synthesized in the gonad, that their levels vary with the reproductive cycle, and that they have a role in the development of gametes.(2) 5-HT receptor formation in the oocyte membrane during oogenesisSerotonin (5-hydroxytryptamine, 5-HT) is a major neurotransmitter that triggers the spawning of bivalve molluscs, mainly their germinal vesicle breakdown (GVBD). The present study employed [3H] 5-HT binding assay to characterize a putative receptor on the prepared oocyte membrane from scallop and oyster and demonstrated the profile and hormonal control of 5-HT receptor formation during their oocyte growth. The dissociation constants of 5-HT on the surfaces of scallop and oyster oocytes were estimated to be 2.64 muM and 2.01 muM,respectively and the maximal binding capacity of each oocyte surface was 152 pmol/mg protein in scallop and 529 pmol/mg protein in oyster. The inhibition of [3H] 5-HT bound by various agonist and antagonist provided the pharmacological profile of 5-HT receptor in each oocyte ; a mixed profile of 5-HT1/5-HT2 in scallop and a relatively single profile of 5-HT1 in oyster. 5-HT receptor formation on the surface of scallop oocyte was induced by estradiol-17beta (E2), which was suggested to be a main reason for promoting effect of E2 on the sensitivity to 5-HT resulting in the induction of spawning. This formation obviously occurred during oocyte growth under the control by E2. Less