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

(1)雌激素在生殖周期中的分布及其在卵巢中的生物合成利用高效液相色谱-电子捕获检测器（HPLC-ECD）在卵巢中检测到雌酮（E1）、雌二醇-17 β（E2）和少量的雌三醇（E3），而在睾丸中仅检测到E2。卵巢中的E2水平始终高于E1，并且随着性成熟而增加。这些结果表明，E2可能在牡蛎和扇贝的生殖事件中发挥作用。体外实验证明，两只双壳贝类的卵巢中都存在17 β-羟类固醇脱氢酶（17 β-HSD）。卵巢中17 β-HSD的活性在产卵后期低于分化早期。通过~ 3 H-水分析法证实了扇贝卵巢中存在芳香化酶活性。3 β-羟基类固醇脱氢酶（3 β-HSD）、P450芳香化酶和E2在沿着生殖小管的细胞中呈阳性反应。结论是雌激素可以 关于我们 这些激素在生殖腺中合成，其水平随生殖周期而变化，并在配子发育中发挥作用。(2)5-羟色胺（5-hydroxytryptamine，5-HT）是双壳类软体动物产卵的主要神经递质，主要是其生殖囊破裂（germinalvesicle breakdown，GVBD）。本研究采用[~ 3 H] 5-HT结合试验对扇贝和牡蛎卵母细胞膜上的5-HT受体进行了表征，并揭示了扇贝和牡蛎卵母细胞生长过程中5-HT受体形成的模式和激素调控。5-HT在扇贝和牡蛎卵母细胞表面的解离常数分别为2.64 μ M和2.01 μ M，最大结合容量分别为152 pmol/mg蛋白和529 pmol/mg蛋白。不同的激动剂和拮抗剂对[~ 3 H] 5-HT结合的抑制作用提供了每个卵母细胞中5-HT受体的药理学分布：扇贝中5-HT 1/5-HT 2的混合分布和牡蛎中5-HT 1的相对单一分布。17 β-雌二醇（E2）可诱导扇贝卵母细胞表面5-HT受体的形成，这可能是E2增强扇贝卵母细胞对5-HT敏感性从而诱导产卵的主要原因。这种形成明显发生在卵母细胞生长过程中的E2控制下。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