中文摘要：

胰岛素样生长因子-I（Insulin-like growth factor-I,IGF-I）是影响脊椎动物生长、发育及代谢的重要调控因子。本研究采用RT-PCR和RACE技术,克隆了银鲳（Pampus argenteus）肝脏IGF-IcDNA序列,应用半定量RT-PCR、Real-time q PCR和原位杂交的方法检测了IGF-I的组织表达特性、在肝脏中的生长表达特性和IGF-I基因在肝脏中的定位。序列分析表明,IGF-I cDNA序列全长836bp,其5′非编码区128bp、3′非编码区92bp,开放阅读框（open reading frame,ORF）605bp,由此推导IGF-I前体蛋白由201个氨基酸组成;前体肽由信号肽、成熟肽、E肽三部分组成,其中信号肽59个氨基酸,成熟肽68个氨基酸,E肽74个氨基酸;成熟肽由B、C、A、D四个区域组成,E肽分析表明,银鲳IGF-I属Ea-4型。同源性比较结果表明,银鲳与同目鲈形目鱼类的IGF-I编码序列同源性较高,为83.52%—91.40%;与哺乳类、鸟类和爬行类的同源性较低。半定量RT-PCR和Real-time q PCR组织特异性表达结果显示,IGF-I m RNA在肝脏组织中的表达量最高,显著高于其它组织,肾脏、心脏、肌肉、脑、鳃、小肠、卵巢次之,嗅球、脾脏和胃中表达较低;半定量RT-PCR和Real-time q PCR不同生长阶段表达结果显示,IGF-I m RNA在30—50g肝脏组织中表达量最高（P〈0.05）;IGF-I m RNA在肝脏中的原位杂交定位结果显示,在肝脏细胞中均有表达,阳性信号主要位于细胞质中,靠近细胞边缘处信号较强。

英文摘要：

Insulin-like growth factor-I （IGF-I） is an important regulator to growth, development, and metabolism of a vertebrate. To clone the IGF-I cDNA sequences in liver of Pampus argenteus, we used RT-PCR （reverse transcription-polymerase chain reaction）, RACE （rapid amplification of cDNA ends）. In addition, to detect the IGF-I expression in the tissues and IGF-I expression levels in the liver in six different growth stages and the positioning of the IGF-I gene in the liver, we used semi-quantitative RT-PCR, quantitative RT-PCR, and in-situ hybridization. Results show that the IGF-I cDNA precursor consists of 836bp with a 605bp open reading frame, ORF, and 5＇ and 3＇ UTR （untranslated regions, 128bp and 92bp, respectively）. Therefore, we deduce that the precursor protein of IGF-I consisted of 201 amino acids; the precursor peptide is composed of signal peptide, mature peptide and E peptide, signal peptide of 59 amino acids, mature peptide of 68 amino acids, and E peptide of 74 amino acids. The mature peptide was composed of four regions B, C, A, and D. Analysis on E peptide showed that IGF-I of pomfret was in Ea-4 type. The IGF-I coding sequence of pomfret had higher identity with the same mesh Perciformes fish, from 83.52% to 91.40%; and lower identity with mammals, birds and reptiles. Semi-quantitative RT-PCR and RT qPCR results show that IGF-I mRNA was expressed in all 10 tissues, high in liver, and low in other tissues. Semi-quantitative RT-PCR and quantitative RT PCR in six different growth stages showed that IGF-I mRNA expression level was the highest when fish weighed between 30-50g, and then decreased significantly between 50-100g （P〈0.05）. The in-situ hybridization to see IGF-I mRNA expression in the liver indicated that GF-I positive cells were found throughout the liver; the signal intensity was significantly higher at cell edge, and positive signals were found mainly in cytoplasm.