甲状腺激素在体外与分离的虹鳟（Salmo gairdneri）肝细胞核的结合：结合亲和力、容量和化学特异性。

Thyroid hormone binding to isolated trout (Salmo gairdneri) liver nuclei in vitro: binding affinity, capacity, and chemical specificity.

作者信息

Bres O, Eales J G

出版信息

Gen Comp Endocrinol. 1986 Jan;61(1):29-39. doi: 10.1016/0016-6480(86)90246-7.

Abstract

Isolated nuclei from trout hepatocytes demonstrated in vitro high-affinity and low-capacity binding for 3,5,3'-tri-iodo-L-thyronine (T3). Binding was reversible; the dissociation rate was 5.7 X 10(-3) min-1 at 15 degrees C. Linear Scatchard plots suggested a single class of noncooperative sites (Kd = 1.4 +/- 0.10 X 10(-10) M; maximum binding capacity (MBC) = 62 +/- 10 fmol/mg DNA). After correction for site degradation, site occupancy by endogenous T3, and the dissociation rate of endogenous bound T3, the MBC was 106 +/- 16 fmol/mg DNA. The T3 affinity exceeded slightly that of the hepatocyte nucleus of the rat; the MBC was lower than for most other vertebrates. The relative binding affinities of thyroid hormone (TH) analogs for the T3 site were: TRIPROP greater than TRIAC greater than methyl-bridged T3 greater than TETRAPROP greater than T3 greater than TETRAC greater than TRIFORM greater than 3,5-dibromo, 3'-isopropyl thyronine greater than L-thyroxine (T4) greater than DL-T4 greater than 3'-isopropyl 3',5'-dimethyl thyronine greater than reverse T3 greater than 3,5-T2. MIT and DIT did not bind at all. This structure-affinity profile was similar but not identical to that of rat liver, indicating considerable but not complete evolutionary conservation of site structure. Parallel studies of T4 binding also indicate a single class of noncooperative sites (Kd = 7.2 +/- 2.4 X 10(-10) M). Both the MBC and the structure-affinity profile for T4 corresponded to those for T3. These observations, combined with the ability of excess T3 or T4 to completely displace both labeled T3 or T4, support a previous suggestion that in teleosts T3 and T4 bind to the same class of nuclear sites. These sites probably represent TH receptors.

摘要

从虹鳟鱼肝细胞分离出的细胞核在体外表现出对3,5,3'-三碘-L-甲状腺原氨酸（T3）具有高亲和力和低容量结合特性。结合是可逆的；在15℃时解离速率为5.7×10⁻³分钟⁻¹。线性Scatchard图表明存在一类非协同位点（解离常数Kd = 1.4±0.10×10⁻¹⁰ M；最大结合容量（MBC）= 62±10 fmol/mg DNA）。在校正位点降解、内源性T3的位点占有率以及内源性结合T3的解离速率后，MBC为106±16 fmol/mg DNA。T3的亲和力略高于大鼠肝细胞的细胞核；MBC低于大多数其他脊椎动物。甲状腺激素（TH）类似物对T3位点的相对结合亲和力为：三碘甲腺原氨酸丙酸酯（TRIPROP）＞三碘乙酸（TRIAC）＞甲基桥联T3＞四碘甲腺原氨酸丙酸酯（TETRAPROP）＞T3＞四碘甲腺原氨酸（TETRAC）＞三碘甲腺原氨酸甲醚（TRIFORM）＞3,5-二溴-3'-异丙基甲状腺原氨酸＞L-甲状腺素（T4）＞DL-T4＞3'-异丙基-3',5'-二甲基甲状腺原氨酸＞反式T3＞3,5-二碘甲状腺原氨酸（T2）。一碘甲腺原氨酸（MIT）和二碘甲腺原氨酸（DIT）根本不结合。这种结构-亲和力图谱与大鼠肝脏的相似但不完全相同，表明位点结构在进化上有相当程度但并非完全的保守性。对T4结合的平行研究也表明存在一类非协同位点（Kd = 7.2±2.4×10⁻¹⁰ M）。T4的MBC和结构-亲和力图谱都与T3的相对应。这些观察结果，再加上过量的T3或T4能够完全取代标记的T3或T4，支持了之前的一种观点，即在硬骨鱼中T3和T4与同一类核位点结合。这些位点可能代表TH受体。