Gopinath R, Walton P E, Etherton T D
Department of Dairy and Animal Science, Pennsylvania State University, University Park 16802.
J Endocrinol. 1989 Feb;120(2):231-6. doi: 10.1677/joe.0.1200231.
The effects of a porcine insulin-like growth factor (IGF)-binding protein on binding of IGF-I and IGF-II to porcine aortic endothelial cells (PAEC) were determined. Binding of 125I-labelled IGF-I and -II to IGF receptors was inhibited by IGF-binding protein. IGF-binding protein inhibited binding of IGF-I and -II in a dose-dependent manner with half-maximal inhibition occurring at 5.43 and 108 micrograms/l respectively. A 125I-labelled IGF-I--IGF-binding protein complex, formed by incubating 125I-labelled IGF-I with IGF-binding protein overnight at 4 degrees C, did not effectively bind to endothelial IGF receptors. Addition of IGF-binding protein to PAEC previously incubated with IGF-I caused a marked dissociation of bound IGF-I (47% dissociation within 12h). These results indicate that the acid-stable IGF-binding protein which appears to be a part of the 150 kDa GH-dependent binding protein, blocks binding of IGF-I and -II by the IGF receptors and appears to exhibit a higher affinity for IGF-I than the endothelial type-I IGF receptor. The ramifications of this latter point with respect to transfer of circulating IGFs (bound to their IGF-binding proteins) across the vascular endothelium are not clear.
测定了一种猪胰岛素样生长因子（IGF）结合蛋白对IGF-I和IGF-II与猪主动脉内皮细胞（PAEC）结合的影响。IGF结合蛋白抑制了125I标记的IGF-I和-II与IGF受体的结合。IGF结合蛋白以剂量依赖的方式抑制IGF-I和-II的结合，半最大抑制浓度分别为5.43微克/升和108微克/升。通过将125I标记的IGF-I与IGF结合蛋白在4℃下孵育过夜形成的125I标记的IGF-I - IGF结合蛋白复合物，不能有效地结合内皮IGF受体。将IGF结合蛋白添加到先前与IGF-I孵育的PAEC中，导致结合的IGF-I明显解离（12小时内解离47%）。这些结果表明，这种酸稳定的IGF结合蛋白似乎是150 kDa生长激素依赖性结合蛋白的一部分，它通过IGF受体阻断IGF-I和-II的结合，并且似乎对IGF-I的亲和力高于内皮I型IGF受体。关于循环中的IGF（与其IGF结合蛋白结合）穿过血管内皮的转移，后一点的影响尚不清楚。
