Amit T, Barkey R J, Bick T, Hertz P, Youdim M B, Hockberg Z
Rappaport Family Research Institute, Faculty of Medicine, Technion, Haifa, Israel.
Mol Cell Endocrinol. 1990 Apr 17;70(2):197-202. doi: 10.1016/0303-7207(90)90159-6.
The present report describes the initial characterization of a specific, high-affinity growth hormone binding protein (GH-BP) in adult male rat serum. GH-BP activity was measured by incubation of rat serum with [125I]hGH and [125I]rGH and separation of bound from free GH by dextran-coated charcoal. [125I]hGH binding to rat serum was dependent on serum concentration and incubation time, equilibrium being reached within 10 min both at 4 and 37 degrees C. Binding was rapidly and completely reversible and specific for somatogenic (but not lactogenic) hormones. Scatchard analysis yielded a linear plot with an affinity (Ka) of 1.51 +/- 0.63 x 10(8) M-1. Preliminary data obtained in various physiological conditions showed that GH-BP activity in adult male rats was 5.95 +/- 0.20%/0.1 ml serum. Significantly higher values were obtained in sera of female (21.66 + 0.79%/0.1 ml serum) and pregnant rats (23.02 +/- 1.15%/0.1 ml serum). A closer analysis of these binding values by Scatchard analysis revealed that the binding capacity in pregnant rats (50.5 +/- 5.8 pmol/0.1 ml serum) was significantly higher than in adult female estrous rats (19.2 +/- 6.5 pmol/0.1 ml serum), both being much higher than in adult male rats (2.5 +/- 0.6 pmol/0.1 ml serum). The GH-BP activity of 10-day-old rats was only approximately 63% of the adult male rat value. The presence of high-affinity GH-specific binding protein in rat serum suggests a probable action in regulation of GH activity. The detailed physiological role of rat serum GH-BP is currently being investigated.
本报告描述了成年雄性大鼠血清中一种特异性、高亲和力生长激素结合蛋白（GH-BP）的初步特征。通过将大鼠血清与[125I]hGH和[125I]rGH孵育，并利用葡聚糖包被的活性炭将结合的GH与游离的GH分离来测定GH-BP活性。[125I]hGH与大鼠血清的结合取决于血清浓度和孵育时间，在4℃和37℃下10分钟内均达到平衡。结合迅速且完全可逆，对促生长（而非促乳）激素具有特异性。Scatchard分析得出线性图，亲和力（Ka）为1.51±0.63×10(8) M-1。在各种生理条件下获得的初步数据表明，成年雄性大鼠的GH-BP活性为5.95±0.20%/0.1 ml血清。在雌性大鼠（21.66 + 0.79%/0.1 ml血清）和妊娠大鼠（23.02±1.15%/0.1 ml血清）的血清中获得的值明显更高。通过Scatchard分析对这些结合值进行更仔细的分析发现，妊娠大鼠的结合能力（50.5±5.8 pmol/0.1 ml血清）明显高于成年雌性动情期大鼠（19.2±6.5 pmol/0.1 ml血清），两者均远高于成年雄性大鼠（2.5±0.6 pmol/0.1 ml血清）。10日龄大鼠的GH-BP活性仅约为成年雄性大鼠值的63%。大鼠血清中高亲和力GH特异性结合蛋白的存在表明其在调节GH活性方面可能具有作用。目前正在研究大鼠血清GH-BP的详细生理作用。
