Conover C A, Baker B K, Hintz R L
Department of Pediatrics, Stanford University, California 94305.
J Clin Endocrinol Metab. 1989 Jul;69(1):25-30. doi: 10.1210/jcem-69-1-25.
Nucleotide sequencing of the two known cDNAs encoding human insulin-like growth factor I (IGF-I) predicts the existence of two different prohormone forms of IGF-I. The E peptide regions extend the carboxy-terminus of IGF-I by either an additional 35 (IGF-IA) or 77 (IGF-IB) amino acids. With a specific and sensitive RIA employing an antiserum directed against a synthetic peptide that is unique to the E peptide region of IGF-IA prohormone (EIA), we have identified EIA-immunoreactive material in the conditioned medium of fetal and postnatal human fibroblasts in culture. Incubation of postnatal human fibroblasts with GH increased specific immunoreactive EIA secretion 2- to 3-fold. There was no immunologically detectable 7.5K IGF-I or IGF-II peptide in acid-chromatographed human fibroblast-conditioned medium under either basal or GH-stimulated conditions. Acid chromatography of human fibroblast-conditioned medium on Sephadex G-75 revealed a single elution peak of EIA immunoreactivity corresponding to a mol wt of 9-17 K. With neutral chromatography, EIA immunoreactivity eluted at 25-38K mol wt. These data suggest that the E peptide region of IGF-IA is translated and released as part of the prohormone form in cultured human fibroblasts, and that the levels of this prohormone are regulated by GH.
对编码人胰岛素样生长因子I（IGF-I）的两个已知cDNA进行核苷酸测序，预测存在两种不同的IGF-I前激素形式。E肽区域使IGF-I的羧基末端额外延伸35个（IGF-IA）或77个（IGF-IB）氨基酸。使用一种特异性和敏感性的放射免疫分析法（RIA），该方法采用针对IGF-IA前激素E肽区域（EIA）特有的合成肽的抗血清，我们在培养的胎儿和出生后人成纤维细胞的条件培养基中鉴定出了EIA免疫反应性物质。将出生后人成纤维细胞与生长激素（GH）一起孵育，可使特异性免疫反应性EIA分泌增加2至3倍。在基础或GH刺激条件下，经酸层析的人成纤维细胞条件培养基中未检测到免疫可检测的7.5K IGF-I或IGF-II肽。在Sephadex G-75上对人成纤维细胞条件培养基进行酸层析，显示出一个对应于9-17K分子量的EIA免疫反应性单一洗脱峰。采用中性层析时，EIA免疫反应性在25-38K分子量处洗脱。这些数据表明，IGF-IA的E肽区域作为前激素形式的一部分被翻译并释放到培养的人成纤维细胞中，并且这种前激素的水平受GH调节。
