Structure and Activity of Fish Growth Hormones

本研究的特点生长激素（GH）的生长刺激潜力分离的两种重要的经济鱼类。从大麻哈鱼（Oncorhynchus凯塔）脑垂体的碱性提取物和鳗鱼（Anguilla japonica）脑垂体的培养基中纯化的生长激素的化学特征。编码这些鱼类GH的cDNA克隆是从垂体多聚腺苷酸（poly（A））<^+ RNA>制备的cDNA文库中分离的，使用的是与激素氨基酸序列相对应的合成DNA。克隆了鲑鱼和鳗鱼生长激素基因的cDNA，并在大肠杆菌中表达。杆菌由基因工程菌合成的鲑鱼和鳗鱼生长激素（重组生长激素）具有与天然生长激素相当的效力。以10- 100 ng/g体重的剂量腹腔注射可刺激鲑科鱼类的生长。重组鲑鱼生长激素溶液浸泡鲑科鱼类， 关于我们 在0.15至1.5 M的浓度下生长<micro>。此外，口服施用重组鲑鱼GH可以刺激幼虹鳟鱼的生长，剂量为10 <micro>g/鱼。采用放射免疫法检测血中生长激素水平。GH在海水适应性鱼类渗透压调节中起重要作用，而催乳素（PRL）在淡水适应性鱼类渗透压调节中起重要作用。由于催乳素显示出与生长激素密切的化学相似性，它们被认为是通过基因复制从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。还表征了鱼PRL。GH和PRL的序列比较显示存在保守的结构，这表明它们可能负责其生物学活性。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