Mechanism of Synthesis and Secretion of Growth Hormone and its Mode of Actions in Telest Fishes

本研究的目的是阐明生长激素（GH）和相关肽，催乳素（PRL）和生长激素（SL）的分泌机制和作用方式，在硬骨鱼特别是参考他们的生活阶段和环境盐度。本研究从硬骨鱼类垂体中分离纯化了GH、PRL和SL，并测定了它们的氨基酸序列和cDNA的碱基序列。建立了放射受体分析和原位杂交方法，以监测血浆和垂体激素水平，并定量测定每种激素的基因表达水平。3.根据血浆动力学研究和器官培养垂体分泌激素的研究，我们已经清楚GH在鲑科鱼类的海水适应中除了促进生长外，还起着重要的作用。另一方面，SL似乎参与钙和脂质代谢以及酸碱平衡。5.在哺乳动物中，GH的作用主要是通过诱导肝脏中胰岛素样生长因子（IGF-I）的产生来实现的，在硬骨鱼中也是如此。然而，生长激素的海水适应效应可能是由本地产生的IFG-I在鳃，可能诱导氯细胞的分化。

The aim of this research project is to clarify mechanisms of secretion and mode of action of growth hormone(GH)and related peptides, prolactin(PRL)and somatolactin(SL), in teleost fishes with special reference to their life stages and environmental salinity. During the last 4 years, the following results were obtained.1.GH, PRL and SL were purified from pituitaries of various teleost species, and their amino acid sequences as well as the base sequences of cDNAs were determined.2.Specific radioimmunoassay, radioreceptorassay and in situ hybridization methods were established to monitor plasma and pituitary hormone levels and to quantify the levels of gene expression for each of he hormones.3.Based on plasma kinetic studies and secretion of the hormones from organcultured pituitary, it has become clear that GH plays an important role in seawater adaptation of salmonid fishes, besides growth promotion.4.PRL's freshwater-adapting effects are well established in various species used in this study. On the other hand, SL seems to be involved in calcium and lipid metabolism as well as in acid-base balance.5.As in mammals, GH's action is exerted primarily by inducing the production of insulin-like growth factor(IGF-I)in the liver also in teleosts. However, seawater-adapting effects of GH are likely to be caused by locally-produced IFG-I in the gill, possibly inducing the differentiation of the chloride cells.