THE CIRCULATING GROWTH-HORMONE (GH)-BINDING PROTEIN COMPLEX - A MAJOR CONSTITUENT OF PLASMA GH IN MAN
THE CIRCULATING GROWTH-HORMONE (GH)-BINDING PROTEIN COMPLEX - A MAJOR CONSTITUENT OF PLASMA GH IN MAN
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DOI：
10.1210/endo-122-3-976
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发表时间：
1988-03-01
期刊：
影响因子：
4.8
通讯作者：
SHAW, MA
中科院分区：
文献类型：
--
作者：
BAUMANN, G;AMBURN, K;SHAW, MA
最近在人血浆中发现了一种与人生长激素(HGH)特异结合的蛋白(HGH)，这表明hGH部分以与结合蛋白结合的复合体的形式循环(S)。然而，生理条件下普遍存在的络合分数的大小是未知的，这是因为1)分析过程中络合物的解离，以及2)放射性标记的hGH与天然hGH结合特性的潜在差异。我们进行了旨在减少分析过程中解离的实验(预标记柱中的凝胶过滤、正面分析和批量分子筛查)，包括天然和放射性碘标记的hGH。对于复杂的分数，三种方法都得出了类似的估计。在正常血浆中，22K hGH的结合分数平均为50.1%(范围39-59%)，20K hGH的结合分数平均为28.5%(范围26-31%)。在约20 ng/ml的hGH水平以上，由于结合蛋白的饱和，结合部分以浓度依赖的方式下降。我们得出结论，循环中的hGH很大一部分是与载体蛋白络合的。这一概念对hGH的代谢、分布和生物活性具有重要的意义。
The recent discovery of a specific binding protein for human GH (hGH) in human plasma suggests that hGH circulates in part as a complex in association with the binding protein(s). However, the magnitude of the complexed fraction prevailing under physiological conditions is unknown because of 1) dissociation of the complex during analysis and 2) potential differences in the binding characteristics of radiolabelled and native hGH. We conducted experiments designed to minimize dissociation during analysis (gel filtration in prelabeled columns, frontal analysis, and batch molecular sieving) with both native and radioiodinated hGH. All three methods yielded similar estimates for the complexed fraction. In normal plasma the bound fraction for 22 K hGH averaged 50.1% (range, 39-59%), that for 20 K hGH averaged 28.5% (range, 26-31%). Above a hGH level of about 20 ng/ml to bound fraction declines in concentration-dependent manner due to saturation of the binding protein. We conclude that a substantial part of circulating hGH is complexed with carrier proteins. This concept has important implications for the metabolism, distribution, and biological activity of hGH.