Höffken B, Ködding R, Von Zur Mühlen A, Hehrmann T, Jüppner H, Hesch R D
Biochim Biophys Acta. 1978 Feb 13;539(1):114-24. doi: 10.1016/0304-4165(78)90126-5.
The nature of the conversion of thyroxine (T4) to triiodothyronine (T3) and reverse triiodothyronine (rT3) was investigated in rat liver homogenate and microsomes. A 6-fold rise of T3 and 2.5-fold rise of rT3 levels determined by specific radioimmunoassays was observed over 6 h after the addition of T4. An enzymic process is suggested that converts T4 to T3 and rT3. For T3 the optimal pH is 6 and for rT3, 9.5. The converting activity for both T3 and rT3 is temperature dependent and can be suppressed by heat, H2O2, merthiolate and by 5-propyl-2-thiouracil. rT3 and to a lesser degree iodide, were able to inhibit the production of T3 in a dose related fashion. Therefore the pH dependency, rT3 and iodide may regulate the availability of T3 or rT3 depending on the metabolic requirements of thyroid hormones.
在大鼠肝脏匀浆和微粒体中研究了甲状腺素（T4）向三碘甲状腺原氨酸（T3）和反三碘甲状腺原氨酸（rT3）转化的性质。加入T4后6小时内，通过特异性放射免疫测定法测定，T3水平升高了6倍，rT3水平升高了2.5倍。提示存在一种将T4转化为T3和rT3的酶促过程。对于T3，最佳pH值为6，对于rT3，最佳pH值为9.5。T3和rT3的转化活性均依赖于温度，并且可被加热、过氧化氢、硫柳汞和5-丙基-2-硫脲嘧啶抑制。rT3以及程度较轻的碘化物能够以剂量相关的方式抑制T3的产生。因此，pH依赖性、rT3和碘化物可能根据甲状腺激素的代谢需求调节T3或rT3的可用性。
