Smith H C, Robinson S E, Eastman C J
Aust J Exp Biol Med Sci. 1980 Apr;58(2):207-12. doi: 10.1038/icb.1980.21.
The study was undertaken to examine the potential intrinsic biological activity of reverse T3 by comparing its binding to nuclear protein in vitro with that of other iodothyronines. Nuclear protein was extracted from normal pig liver using methods described for rat tissues. At 25 degrees 30% of the added 125I rT3 was specifically bound to the nuclear protein. The order of potency in displacing 125I rT3 was rT3 > 3'5'T2 > T4 > T3 > 3,3'T2 > 3,5T2. This contrasted with the order of potency in displacing 125I T3 which was T3 > T4 > 3,3'T2 > 3,5T2 > rT3 > 3'5'T2. This difference in the hierarchy of iodothyronine binding is consistent with binding of these radioligands to different components of the nuclear protein extract. These experiments demonstrate separate binding components of nuclear protein for T3 and rT3 in a thyroid hormone responsive tissue and may be relevant to the mechanism of action of thyroid hormones.
本研究旨在通过比较反式三碘甲状腺原氨酸（reverse T3，rT3）与其他碘甲状腺原氨酸在体外与核蛋白的结合情况，来检测rT3潜在的内在生物活性。采用针对大鼠组织所描述的方法从正常猪肝中提取核蛋白。在25摄氏度时，所添加的125I rT3中有30%特异性结合到核蛋白上。取代125I rT3的效力顺序为rT3 > 3'5'二碘甲腺原氨酸（3'5'T2）> 甲状腺素（T4）> 三碘甲状腺原氨酸（T3）> 3,3'二碘甲腺原氨酸（3,3'T2）> 3,5二碘甲腺原氨酸（3,5T2）。这与取代125I T3的效力顺序形成对比，后者为T3 > T4 > 3,3'T2 > 3,5T2 > rT3 > 3'5'T2。碘甲状腺原氨酸结合层级的这种差异与这些放射性配体与核蛋白提取物不同成分的结合情况一致。这些实验证明了在甲状腺激素反应性组织中，核蛋白对于T3和rT3存在不同的结合成分，这可能与甲状腺激素的作用机制相关。
