免疫吸着剤を用いた血清TBGと甲状腺ホルモンとの相互作用の研究:(1) 健常人と妊婦でのTBGとT4のKa値の検討

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A very simple method for the evaluation of the interaction between thyroxine binding globulin (TBG) and thyroxine (T4) has been developed and evaluated in 6 healthy subjects and 5 pregnant women. Rabbit anti-human TBG antiserum was precipitated with 50% anmonium sulfate followed by passing a DEAE-cellulose column. Immunoglobulin G (IgG) fraction thus prepared was covalently attached on a Sepharose CL-4B and used as an immunoadsorbent of serum TBG. After treatment with charcoal to remove endogeneous thyroid hormones, 10 μl of sera from 6 healthy subjects and 5 pregnant women were incubated with 125I-T4 and various concentrations of cold T4 followed by immunoadsorption with anti-TBG-Sepharose, and association constants (Ka) between TBG and T4 were calculated in each subject using Scatchard's plot. The Ka value thus obtained in 6 healthy subjects was 1.47 × 108M-1 (SD = 0.24), and in 5 pregnant women it was 0.82 × 108M-1 (SD = 0.21) which was significantly lower than that of healthy subjects (P<0.001). Our present method does not need purification of TBG from serum to investigate its functions, especially in relation to the binding with thyroid hormones. Also, only a very small amount (100-150 μl) of serum is enough for the calculation of Ka between T4 and TBG. The whole procedure is very easy to perform and can be done in a relatively short time, and therefore we consider this method clinically relevant and useful.
日本内分泌学会の論文