Structure and Activity of Fish Growth Hormones

本研究鉴定了从两种重要经济鱼类中分离的生长激素（GH）的促生长潜能。从大马哈鱼（Oncorhynchus keta）脑垂体碱性提取物和鳗鲡（Anguilla japonica）脑垂体培养基中纯化的GHs进行了化学表征。从垂体poly(A) <^+RNAs> cDNA文库中分离到编码这些GHs的cDNA克隆，合成了与激素氨基酸序列相对应的dna。克隆了三文鱼和鳗鱼生长激素的cdna，并在大肠杆菌中进行了表达。由基因工程细菌合成的三文鱼和鳗鱼GHs（重组GHs）具有与天然GHs相当的效力。腹腔注射10-100ng/g体重的剂量可刺激鲑鱼生长。研究了给鱼施用这些激素的可能途径。将重组鲑鱼生长激素溶液浸泡在0.15 ~ 1.5 <微> g/鱼的浓度下，可刺激虹鳟鱼幼鱼的生长，而口服重组鲑鱼生长激素在10 <微> g/鱼的浓度下可刺激虹鳟鱼幼鱼的生长。用鲑鱼生长激素放射免疫法检测血液中生长激素的水平。在给药后15-18小时显著增加。GHs对海水适应鱼类的渗透压起重要调节作用，而催乳素（PRL）对淡水适应鱼类的渗透压起调节作用。我们工作的第二个主要目标是研究重要的调节激素的结构-功能关系。由于prl在化学上与生长激素相似，它们被认为是通过基因复制从一个共同的祖先分子进化而来的。以便更好地了解分子进化或结构-功能关系。鱼类prl也有特征。GHs和prl的序列比较表明，它们存在保守结构，可能与它们的生物活性有关。根据序列比较，估计GH和PRL从共同祖先分子分化的时间约为5亿年前。少

This investigation characterized the growth stimulating potential of growth hormones (GH) isolated form two species of economically important fish. GHs purified from an alkaline extract of chum salmon (Oncorhynchus keta) pituitary glands and from a culture medium of eel (Anguilla japonica) pituitary glands were chemically characterized. cDNA clones encoding these fish GHs were isolated from cDNA libraries prepared from pituitary gland poly(A) <^+RNAs> , using synthetic DNAs corresponding to the amino acid sequence of the hormones. The cDNAs of salmon and eel GH were cloned and expressed in E. coli. Salmon and eel GHs synthesized by genetically engineered bacteria (recombinant GHs) had potency equivalent to the natural GHs. Salmonid growth could be stimulated by intraperitoneal injections at doses of 10-100ng/g body weight.Possible routes for administration of these hormones to fish were investigated. Immersion of salmonid fish into solution of the recombinant salmon GH stimulated the g … More rowth at concentrations of 0.15 to 1.5 <micro> M. Furthermore, oral administration of the recombinant salmon GH could stimulate growth of young rainbow trout at a dose of 10 <micro> g/fish. The blood level of GH, detected by salmon GH radioimmunoassay. increased significantly at 15-18 hour after the administration.It was also confirmed that GHs play an important role in regulating osmotic pressure of seawater-adapting fish, while prolactin (PRL) regulates osmotic pressure in freshwater-adapting fish.A second major goal of our work was to study structure-function relationships of the important regulatory hormone. Since PRLs show close chemical resemblance to GH, they have been thought to have evolved from a common ancestral molecule by gene duplication. In order to obtain better insight into the molecular evolution or structure-function relationships. fish PRLs were also characterized. The sequence comparisons of GHs and PRLs showed the occurrence of conserved structures, suggesting that they may be responsible for their biological activities. On the basis of the sequence comparison, the time of divergence of GH and PRL from the common ancestral molecule was estimated to be about 500 million years ago. Less