Studies of the function and gene of somatolactin, a new pituitary hormone

该项目的目标是建立一种新的垂体蛋白——生长肌动素，作为一种热带激素。生长肌动素（Somatolactin， SL）是硬骨鱼生长激素（GH）和催乳素（PRL）家族的新成员。已鉴定出大西洋鳕鱼、比目鱼、鲑科、金头鱼、鲤鱼和槽鱼的SLs，以及比目鱼、大西洋鳕鱼和鲑鱼的slcdna。目前所分析的SL序列比较表明，该蛋白比对应物种的GHs具有更高的保守性。用特异性抗血清免疫组化发现，鳕鱼和大多数其他硬骨鱼的ars中间体的周期性酸转移阳性细胞以及鲑科鱼的pars中间体的嗜色细胞中都存在SL。免疫组化电镜观察发现，虹鳟鱼细胞的分泌颗粒上主要存在a -金复合物。开发并验证了一种针对鲑鱼SL的同源放射免疫分析方法。在coho slmn生殖成熟的最后一年，将虹鳟鱼从富含钙的淡水转移到淡水，以及将虹鳟鱼暴露于酸性水后，观察到血浆SL水平升高。这些发现表明SL调节生殖、钙代谢和酸碱平衡。与哺乳动物GH/PRL基因一样，鲑鱼SL基因由5个外显子组成，但与具有6个外显子的鲑鱼GH基因不同。在转录起始位点上游发现了1个TATA box和4个与Pit-1结合元件相对应的共识序列，这是哺乳动物GH和PRL基因表达所必需的。结果表明，鲑鱼的Pit-1 mRNA编码365个氨基酸，比大鼠的Pit-1多74个残基。利用对chum samon Pit-1的抗体，发现该蛋白位于pars培养基中产生sl细胞的细胞核中。在HeLa细胞共切实验中，Pit-1增强了促进子

The goal of the roject is to stablish a newy fund pituitary protein, somatolactin, as a tropic hormone. Somatolactin (SL) is a new hypophysial member of growth hormone (GH) and prolactin (PRL) family of teleosts. SLs of Atantic cod, flunder, salmonids, gilthead, carp, and channel catfsh, and SLcDNAs of flunder, Atantic cod, and chum salmon have been identified. Comparison of the SL sequences so far analyzed indicates that this protein is highly conserved, more so than the GHs from the corresponding species. Immunhistochemistry with a specific antiserum to cod SL revealed that SL is present in periodic-acid-Shiff-positive cells of the ars intermeda in cod and mst other teleost species, and in chromophoic cells of the pars intermedia in salmonids. By an eectron-microscopic immunohistochemistry protein A-gold complex s localized mostly on the secretory granules of these cels of rainbow trout. A homologous radio-immunoassay specific for salmon SL was deeloped and validated. Increases of plasma SL levels have been bserved, during the final year of reroductive maturation of coho slmn, after transfer rainbow trout from Ca-rich fresh water to fresh water, and after exposure rainbow trout to acidic waer. These findings suggest that SL regulates reproduction, Ca-metabolism, and acid-base balance. Salmon SL gene was comprised of five exones as in the case of mammalian GH/PRL gees, but was ulike salmnid GH genes, which have 6 exones. Upstream from the transcriptional initiation site were found one TATA box and four consensus sequences corresponding to the Pit-1 binding element, which is known to be essential to expression of mammalian GH and PRL genes. Salmon Pit-1 mRNA was found to encode a 365 amino acid protein, which was 74 residues larger than that of rat Pit-1. Using antibody against chum samon Pit-1, this protein was shwn to be located in the nuclei in the SL-producing cells in the pars intermedia. In experments of cotransection into HeLa cells, Pit-1 enhanced the promo