| Co-Investigator(Kenkyū-buntansha) |
KANEKO Toyoji Univ. Tokyo, Ocean Res. Inst., Assis. Prof., 海洋研究所, 助手 (70221190)
AIDA Katumi Univ. Tokyo, Fac. of Agr., Prof, 農学部, 教授 (50012034)
KAWAUTI Hiroshi Kitasato Univ, School of Fish., Prof, 水産学部, 教授 (70050523)
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| Research Abstract |
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.
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