Lemarchand-Béraud T H, Holm A C, Scazziga B R
Acta Endocrinol (Copenh). 1977 May;85(1):44-54. doi: 10.1530/acta.0.0850044.
In an investigation of thyroxine (T4) and triiodothyronine (T3) receptors in humans, the lymphocyte was chosen as the target cell. This study was performed to elucidate whether T3 and T4 bind to different receptors, if T4 is bound only after conversion into T3, and whether there is any modification of the receptors in hyper- and hypothyroidism. Lymphocytes were found to possess a high-affinity, limited-capacity bindings sites for both T4 and T3. The mean equilibrium affinity constant (Ka) was 2.28-10(10 +/- 0.21 m-1 for T3, and 0.98 - 10(10) +/- 0.16 m-1 for T4. The mean number of saturable binding sites was 115 for T3, and 102 for T4. The binding capacities and affinities also determined in the lymphocyte nuclei isolated after incubation of the intact cell, were similar to those observed in the intact cells. In competition experiments, labelled T4 was as readily displaced by T3 as by T4 itself, whereas labelled T3 was displaced only by a 40 times higher concentration of T4 than T3. These observations suggest identical receptors for the two hormones and a binding of T4 as such, provided it is not in competition with T3. In lymphocytes from hyperthyroid patients, receptor affinities and numbers remained unchanged. In lymphocytes from hypothyroid patients, the affinity was normal, but the mean number of T3 binding sites was increased to 310 (P less than 0.0001), to return to normal after a few months of treatment.
在一项对人体甲状腺素（T4）和三碘甲状腺原氨酸（T3）受体的研究中，淋巴细胞被选为靶细胞。进行这项研究是为了阐明T3和T4是否与不同的受体结合，T4是否仅在转化为T3后才被结合，以及甲状腺功能亢进和减退时受体是否有任何改变。研究发现淋巴细胞对T4和T3都具有高亲和力、有限容量的结合位点。T3的平均平衡亲和常数（Ka）为2.28×10¹⁰±0.21m⁻¹，T4的平均平衡亲和常数（Ka）为0.98×10¹⁰±0.16m⁻¹。T3的可饱和结合位点平均数为115个，T4为102个。在完整细胞孵育后分离的淋巴细胞核中测定的结合能力和亲和力与在完整细胞中观察到的相似。在竞争实验中，标记的T4被T3取代的程度与被T4自身取代的程度相同，而标记的T3仅被浓度比T3高40倍的T4取代。这些观察结果表明这两种激素具有相同的受体，并且T4本身可以结合，前提是它不与T3竞争。在甲状腺功能亢进患者的淋巴细胞中，受体亲和力和数量保持不变。在甲状腺功能减退患者的淋巴细胞中，亲和力正常，但T3结合位点的平均数增加到310个（P＜0.0001），治疗几个月后恢复正常。
