Structure and Activity of Fish Growth Hormones

研究了从两种重要经济鱼类中分离出的生长激素(GH)的促生长潜力。从鲑鱼(Oncorhynchus Keta)脑垂体的碱性提取物和鳗鱼(Anguilla Japan Onica)脑垂体的培养液中提纯了GHS，并对其进行了化学表征。利用与激素氨基酸序列相对应的合成DNA，从垂体腺Poly(A)&lt；^+RNAs&gt；的cDNA文库中分离到编码这些鱼类GHS的cDNA克隆。克隆了鲑鱼和鳗鱼生长激素基因，并在大肠杆菌中进行了表达。由基因工程菌合成的三文鱼和鳗鱼GHS具有与天然GHS相当的效力。按10-100 ng/g体重的剂量腹腔注射可刺激鲑鱼的生长，并对这些激素给鱼的可能途径进行了研究。重组鲑鱼生长激素溶液浸泡鲑鱼对g-…的刺激作用此外，口服重组鲑鱼生长激素10 mg/尾可促进虹鱼幼鱼的生长。用鲑鱼生长激素放射免疫法测定血中生长激素水平。同时也证实了GHS在海水适应性鱼类渗透压调节中起重要作用，而催乳素(PRL)对淡水适应性鱼类渗透压具有调节作用。由于PRL在化学上与GH非常相似，它们被认为是由一个共同的祖先分子通过基因复制进化而来的。以便更好地洞察分子进化或结构-功能关系。对鱼类PRL也进行了表征。GHS和PRLS的序列比较表明，它们存在保守结构，这表明它们可能与它们的生物学活性有关。在序列比较的基础上，GH和PRL与共同祖先分子的分歧时间估计为约5亿年前。较少

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