Goldfine I D, Amir S M, Ingbar S H, Tucker G
Biochim Biophys Acta. 1976 Sep 21;448(1):45-56. doi: 10.1016/0005-2736(76)90075-4.
The binding of biologically active [125I]thyrotropin to purified plasma membranes prepared from bovine thyroid glands was studied. At 4 degrees C, specific binding reached a maximum after 2 h of incubation and a plateau was maintained for up to 20 h. Degradation of [125I]thyrotropin was undetectable after 2 h of incubation and was only 10% of the total after 20 h. At pH 6.0, at which binding was maximal, a single class of binding sites, having a dissociation constant of approx. 25 nM, was evident. Dissociation studies revealed first order kinetics with a half-time of 2-3 min. At pH 7.5, binding curves were complex, suggesting two orders of binding sites with dissociation constants of approx. 200 nM and 80 pM. Further, at this pH, dissociation of the thyrotropin from its receptor was also complex, suggesting the presence of two first order reactions, one with a half-time similar to that seen at pH 6.0 and another with a half-time of 4 h. At both pH 6.0 and 7.5, insulin, glucagon, growth hormone, and prolactin were without effect on [125I]thyrotropin binding. Similar high affinity and low affinity binding sites were seen with porcine thyroid membranes, but only low affinity sites were seen with either rat liver membranes or human cultured lymphocytes.
研究了生物活性[125I]促甲状腺激素与从牛甲状腺制备的纯化质膜的结合。在4℃下，孵育2小时后特异性结合达到最大值，并维持平台期长达20小时。孵育2小时后未检测到[125I]促甲状腺激素的降解，20小时后仅占总量的10%。在结合最大的pH 6.0时，明显存在一类解离常数约为25 nM的结合位点。解离研究显示一级动力学，半衰期为2 - 3分钟。在pH 7.5时，结合曲线复杂，表明存在两类结合位点，解离常数约为200 nM和80 pM。此外，在此pH下，促甲状腺激素从其受体的解离也很复杂，表明存在两个一级反应，一个半衰期与在pH 6.0时相似，另一个半衰期为4小时。在pH 6.0和7.5时，胰岛素、胰高血糖素、生长激素和催乳素对[125I]促甲状腺激素结合均无影响。猪甲状腺膜也观察到类似的高亲和力和低亲和力结合位点，但大鼠肝膜或人培养淋巴细胞仅观察到低亲和力位点。
