Pekonen F, Weintraub B D
J Biol Chem. 1980 Sep 10;255(17):8121-7.
Thyropin binding to high affinity receptors on human and porcine membranes was studied at pH 7.4, 37 degrees C, in 10 mM Tris-HCl, 150 mM NaCl, 0.1% albumin. By preincubating the membranes in high salt concentration before binding studies, the number of high affinity receptors could be increased 4- to 8-fold. The salt-induced exposure of high affinity TSH receptors was pH- and temperature-dependent and was maximal at pH 5.0, 37 degrees C in the presence of 1 M (NH4)2SO4. Other salts tested, including NaCl, HN4Cl, and Na2SO4, were also able to increase high affinity THS binding. The receptors exposed by salt were indistinguishable from those present on the membranes before such treatment. They had an affinity constant of 0.5 to 1 X 10(10 M-1, and a high TSH specificity with no inhibition of 125I-TSH binding in the presence of a thousandfold excess of gamma-globulin, thyroglobulin, corticotropin, cholera toxin, and gangliosides. Thyrotropin binding to low affinity TSH binding sites (affinity constant 1 to 3 X 10(7) M-1) measured at pH 6.0, 4 degrees C in 10 mM Tris/acetate, 0.1% albumin was unaltered by pre-exposure of membranes to high salt concentrations. These receptors had low TSH specificity and binding was inhibited by gamma-globulin, thyroglobulin, cholera toxin, and gangliosides. The salt-induced selective exposure of high affinity receptors with unaltered number of low affinity sites is further support for the existence of two separate TSH binding sites on thyroid membranes.
在pH 7.4、37℃、含有10 mM Tris-HCl、150 mM NaCl和0.1%白蛋白的条件下，研究了促甲状腺激素与人及猪细胞膜上高亲和力受体的结合情况。在结合研究之前，通过在高盐浓度下对细胞膜进行预孵育，高亲和力受体的数量可增加4至8倍。盐诱导的高亲和力促甲状腺激素受体暴露呈pH值和温度依赖性，在pH 5.0、37℃、存在1 M硫酸铵的情况下达到最大值。所测试的其他盐，包括氯化钠、氯化铵和硫酸钠，也能够增加高亲和力促甲状腺激素的结合。盐暴露后的受体与处理前细胞膜上存在 的受体没有区别。它们的亲和常数为0.5至1×10¹⁰ M⁻¹，对促甲状腺激素具有高特异性，在存在千倍过量的γ球蛋白、甲状腺球蛋白、促肾上腺皮质激素、霍乱毒素和神经节苷脂的情况下，不抑制¹²⁵I-促甲状腺激素的结合。在pH 6.0、4℃、含有10 mM Tris/醋酸盐和0.1%白蛋白的条件下测量的促甲状腺激素与低亲和力促甲状腺激素结合位点（亲和常数为1至3×10⁷ M⁻¹）的结合，不受细胞膜预先暴露于高盐浓度的影响。这些受体的促甲状腺激素特异性较低，其结合受到γ球蛋白、甲状腺球蛋白、霍乱毒素和神经节苷脂的抑制。盐诱导的高亲和力受体选择性暴露而低亲和力位点数量不变，进一步支持了甲状腺细胞膜上存在两个独立的促甲状腺激素结合位点。
