Massa G, Mulumba N, Ketelslegers J M, Maes M
Unité de Diabétologie et Nutrition, University of Louvain, School of Medicine, Brussels, Belgium.
Endocrinology. 1990 Apr;126(4):1976-80. doi: 10.1210/endo-126-4-1976.
The in vitro binding of 125I-bovine growth hormone (bGH) to adult rat serum was studied using Ultrogel AcA34 filtration. When analytical chromatography on a 1.6 x 100 cm column was performed, four peaks of radioactivity were revealed: the first two peaks with Mr +/- 220,000 and +/- 110,000 corresponded to bound 125I-bGH (abolished by excess of unlabeled bGH), the third corresponded to free 125I-bGH and the fourth to free Na125I (Vt). On a short (1 x 40 cm) column, bound 125I-bGH eluted as a single peak between the void volume (Vo) and the peak of free 125I-bGH. Serum 125I-bGH binding was specific, saturable, and time-dependent. Specific serum 125I-bGH binding (bound/total radioactivity x 100), calculated as the difference of binding in the absence and the presence of an excess unlabeled bGH, was higher in female than in male rats (26 +/- 2% vs. 11 +/- 1%, respectively; mean +/- SE; n = 6; P less than 0.01). Scatchard analysis revealed a binding affinity of 2 x 10(8) M-1 for both sexes, and a binding capacity of 6.4 x 10(-8) mol/liter for the female rats and 1.6 x 10(-8) mol/liter for the male rats (mean of three serum pools of three animals each). Specific binding of 125I-bGH to serum correlated significantly with 125I-bGH binding to liver homogenates (r = 0.83; n = 12; P less than 0.01). These results suggest the presence of a specific GH-binding protein in rat serum and provide further evidence for a close relationship between serum GH-binding protein and hepatic GH receptors.
采用Ultrogel AcA34凝胶过滤法研究了125I-牛生长激素（bGH）与成年大鼠血清的体外结合情况。在1.6×100 cm的柱上进行分析性色谱分析时，出现了四个放射性峰：前两个峰的相对分子质量（Mr）分别约为220,000和110,000，对应于结合的125I-bGH（可被过量未标记的bGH消除），第三个峰对应游离的125I-bGH，第四个峰对应游离的Na125I（Vt）。在短柱（1×40 cm）上，结合的125I-bGH在空体积（Vo）和游离125I-bGH峰之间以单一峰洗脱。血清对125I-bGH的结合具有特异性、可饱和性且与时间相关。特异性血清125I-bGH结合率（结合的放射性/总放射性×100），计算为在无过量未标记bGH和有过量未标记bGH存在时结合率的差值，雌性大鼠高于雄性大鼠（分别为26±2%和11±1%；均值±标准误；n = 6；P<0.01）。Scatchard分析显示，两性的结合亲和力均为2×108 M-1，雌性大鼠的结合容量为6.4×10-8 mol/L，雄性大鼠为1.6×10-8 mol/L（每组三只动物的三个血清池的均值）。125I-bGH与血清的特异性结合与125I-bGH与肝匀浆的结合显著相关（r = 0.83；n = 12；P<0.01）。这些结果提示大鼠血清中存在一种特异性生长激素结合蛋白，并为血清生长激素结合蛋白与肝生长激素受体之间的密切关系提供了进一步证据。
