Rooda S J, van Loon M A, Visser T J
J Clin Invest. 1987 Jun;79(6):1740-8. doi: 10.1172/JCI113014.
Reverse triiodothyronine (rT3) is metabolized predominantly by outer ring deiodination to 3,3'-diiodothyronine (3,3'-T2) in the liver. Metabolism of rT3 and 3,3'-T2 by isolated rat hepatocytes was analyzed by Sephadex LH-20 chromatography, high performance liquid chromatography, and radioimmunoassay, with closely agreeing results. Deiodinase activity was inhibited with propylthiouracil (PTU) and sulfotransferase activity by sulfate depletion or addition of salicylamide or dichloronitrophenol. Normally, little 3,3'-T2 production from rT3 was observed, and 125I- was the main product of both 3,[3'-125I]T2 and [3',5'-125I]rT3. PTU inhibited rT3 metabolism but did not affect 3,3'-T2 clearance as explained by accumulation of 3,3'-T2 sulfate. Inhibition of sulfation did not affect rT3 clearance but 3,3'-T2 metabolism was greatly diminished. The decrease in I- formation from rT3 was compensated by an increased recovery of 3,3'-T2 up to 70% of rT3 metabolized. In conclusion, significant production of 3,3'-T2 from rT3 by rat hepatocytes is only observed if further sulfation is inhibited.
反式三碘甲状腺原氨酸（rT3）主要在肝脏中通过外环脱碘代谢为3,3'-二碘甲状腺原氨酸（3,3'-T2）。通过葡聚糖凝胶LH-20色谱法、高效液相色谱法和放射免疫分析法分析了分离的大鼠肝细胞对rT3和3,3'-T2的代谢情况，结果高度一致。用丙硫氧嘧啶（PTU）抑制脱碘酶活性，通过耗尽硫酸盐或添加水杨酰胺或二氯硝基苯酚抑制磺基转移酶活性。正常情况下，从rT3观察到的3,3'-T2生成量很少，125I-是3,[3'-125I]T2和[3',5'-125I]rT3的主要产物。PTU抑制rT3代谢，但不影响3,3'-T2清除，这可由3,3'-T2硫酸盐的积累来解释。抑制硫酸化不影响rT3清除，但3,3'-T2代谢大大减少。rT3生成I-的减少通过3,3'-T2回收率的增加得到补偿，高达代谢的rT3的70%。总之，只有在进一步的硫酸化受到抑制时，才会观察到大鼠肝细胞从rT3大量生成3,3'-T2。
