Growth stimulation in abalone by salmon growth hormone and mechanism of its growth

本研究旨在通过在早期进化的脊椎动物软骨鱼和Agnatha中鉴定生长激素（GH）蛋白和cDNA，以及在无脊椎动物鲍鱼中鉴定GH样蛋白或基因，来估计生长激素（GH）家族的起源和进化，并将这些发现应用于鲍鱼养殖。生长激素家族由生长激素、催乳素（PRL）和生长激素（SL）组成。我们从角鲨和七鳃鳗的脑垂体中分离出了183个残基的GH和181个残基的GH，并克隆了它们的cdna。然而，我们没有获得在七鳃鳗中存在PRL和SL的证据。我们还从七鳃鳗的肝脏中克隆了一个胰岛素样生长因子（IGF） cDNA，并在体外肝脏中证明了其mRNA表达的剂量依赖性增加。因此，很可能通过GH和IGF轴在早期进化的脊椎动物中建立了生长加速机制，并且在Agnatha的进化过程中复制了一个GH基因，并在颌口动物中分化为PRL和SL。我们在无脊椎动物中寻找类似gh的蛋白质。使用鲑鱼生长激素抗体，我们在鲍鱼的大脑神经节中发现了GH免疫阳性细胞。从该组织中，我们用PCR方法克隆了一个cDNA片段，引物与GH最保守的c端区相对应。推导出的44个氨基酸序列与GH高度相似。这表明无脊椎动物可能有一种类似gh的蛋白质。然后我们观察了鲑鱼生长激素对鲍鱼生长的影响。用含有鲑鱼生长激素的海藻酸凝胶饲喂幼鲍鱼。饲喂这种凝胶后，在鲍鱼的体液中检测到相当水平的鲑鱼生长激素。与对照动物相比，鲍鱼的壳长和重量显著增加。因此，鲑鱼生长激素凝胶可能是一种潜在的鲍鱼生长加速剂。

This study aimed to estimate the origin and evolution of the growth hormone (GH) family following the identification of the GH protein and cDNA in the early-evolved vertebrates, Chondrichthyes and Agnatha, and a GH-like protein or gene in an invertebrate, the abalone, and apply these findings to abalone aquaculture.The GH family is composed of GH, prolactin (PRL) and somatolactin (SL). We have isolated dogfish GH (183 residues) and lamprey GH (181 residues) from their pituitary glands and cloned their cDNAs. We did not, however, obtain evidences for the presence of PRL and SL in the lamprey. We have also cloned an insulin-like growth factor (IGF) cDNA from the lamprey liver and demonstrated a dose-dependent increase of its mRNA expression in the liver in vitro. Therefore, it is likely that the growth-acceleration mechanism through the GH and IGF axis was established in the early-evolved vertebrates, and that a GH gene was duplicated during the evolution of Agnatha and diversified into PRL and SL in the gnathostomes. We searched for a GH-like protein in invertebrates. Using an antibody to salmon GH, we found GH-immunopositive cells in the cerebral ganglia of abalone. From this tissue, we cloned a cDNA fragment by PCR with primers corresponding to the most conserved C-terminal region of GH. The deduced 44 amino acids sequence is highly similar to that of GH. This suggests that invertebrates may have a GH-like protein. We then looked at the effect of salmon GH on the growth of abalone. Juvenile abalone were fed with alginic acid-gel which contained salmon GH. After feeding with this gel, considerable levels of salmon GH were detected in the body fluids of the abalone. The shell length and weight of the abalone increased remarkably in comparison with the control animals. Thus, the salmon GH gel may be a potential a growth accelerating agent for the abalone.