Smallridge R C, Whorton N E
Metabolism. 1984 Nov;33(11):1034-8. doi: 10.1016/0026-0495(84)90233-6.
Characteristics of 3'-monoiodothyronine (3'-T1) degradation were examined in vitro in rat tissue homogenates. In rat liver homogenates, 3'-T1 degradation was optimal at pH 7.4, and was dependent upon time, temperature, and tissue concentration. The Michaeli's constant (Km) = 0.84 mumol/L. 3'-T1 degradation was enhanced by dithiothreitol and inhibited by propylthiouracil, sodium ipodate, ANS, and sodium azide but not by methimazole. Animals that fasted for three days had significant reductions in both hepatic T4 to T3 conversion (199 +/- 12 v 116 +/- 12 pg T3 generated/mg protein; P less than 0.001) and 3'-T1 degradation (588 +/- 31 v 148 +/- 53 pg 3'-T1 degraded/mg protein; P less than 0.001). To document that 3'-T1 degradation was occurring by deiodination, both liver and kidney homogenates were incubated with 125I-3'-T1 (approximately 3 microCi; 13.1 nmol/L). The reaction products were separated on a reverse-phase high pressure liquid chromatography (HPLC) column. In both tissues an iodide peak was generated, and no other radiolabeled peaks appeared except for 125I-3'-T1. These data suggest that 3'-T1 is metabolized by phenolic-ring monodeiodination and is enzymic in nature.
在大鼠组织匀浆中对3'-单碘甲腺原氨酸（3'-T1）的降解特性进行了体外研究。在大鼠肝脏匀浆中，3'-T1降解在pH 7.4时最为适宜，且依赖于时间、温度和组织浓度。米氏常数（Km）=0.84 μmol/L。二硫苏糖醇可增强3'-T1降解，而丙硫氧嘧啶、胆影酸钠、ANS和叠氮化钠可抑制其降解，但甲巯咪唑无此作用。禁食三天的动物肝脏中T4向T3的转化（每毫克蛋白生成的T3：199±12对116±12 pg；P＜0.001）和3'-T1降解（每毫克蛋白降解的3'-T1：588±31对148±53 pg；P＜0.001）均显著降低。为证明3'-T1降解是通过脱碘发生的，将肝脏和肾脏匀浆与125I-3'-T1（约3 μCi；13.1 nmol/L）一起孵育。反应产物在反相高压液相色谱（HPLC）柱上分离。在两种组织中均产生了一个碘化物峰，除125I-3'-T1外未出现其他放射性标记峰。这些数据表明3'-T1通过酚环单脱碘代谢，且本质上是酶促反应。
