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

本研究旨在通过对软骨鱼类和无颌鱼类生长激素（GH）蛋白和cDNA以及无脊椎动物鲍鱼生长激素样蛋白和基因的鉴定，探讨生长激素（GH）家族的起源和进化，并将其应用于鲍鱼养殖。我们从角鲨和七鳃鳗的脑垂体中分离出GH（183个残基）和GH（181个残基），克隆了它们的cDNA。然而，我们并没有获得证据的存在，PRL和SL的七鳃鳗。我们还从七鳃鳗肝脏中克隆了胰岛素样生长因子（IGF）cDNA，并证明其mRNA在体外肝脏中的表达呈剂量依赖性增加。因此，这是可能的生长加速机制，通过GH和IGF轴建立在早期进化的脊椎动物，GH基因复制无颌类的进化过程中，并多样化成PRL和SL的有颌类。我们在无脊椎动物中寻找GH样蛋白。使用鲑鱼生长激素的抗体，我们发现生长激素免疫阳性细胞在脑神经节的鲍鱼。从这个组织中，我们克隆了一个cDNA片段，通过PCR与引物对应的最保守的C-末端区域的生长激素。推导的44个氨基酸序列与GH高度相似。这表明无脊椎动物可能具有GH样蛋白。然后，我们研究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。用这种凝胶喂养后，在鲍鱼的体液中检测到相当水平的鲑鱼生长激素。与对照组相比，鲍鱼的壳长和壳重显著增加。因此，鲑鱼生长激素凝胶可能是一种潜在的鲍鱼生长促进剂。

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.