Taurog A, Riesco G, Larsen P R
Endocrinology. 1976 Jul;99(1):281-90. doi: 10.1210/endo-99-1-281.
It was observed in the present investigation that labeled thyroxine (T4) comprised less than 2% of the total 131I in the thyroids of severely iodine-deficient rats labeled with 131I for 18-24 h, a much lower value than had previously been reported for iodine-deficient rats. This low value was attributable to two factors: 1) the use of a diet low enough in iodine content to produce extreme iodine deficiency, and 2) the use of a paper chromatography system that successfully separates T4 from the minor iodothyronines, 3,3'-diiodothyronine (T2) and 3',5',3-triiodothyronine (reverse T3; T3'). Formation of the minor iodothyronines, while low, becomes appreciable in relation to T4 formation in severe iodine deficiency. In the present study, the formation of labeled T2 was significant only in iodine deficiency, and the highest values were observed in the most severely iodine-deficient rats. In the latter, labeled monoiodotyrosine (MIT) comprised approximately 60% of the total 131I in the thyroid, and the increased formation of T2 could be attributed to the increased probability of coupling between two molecules of MIT. The formation of labeled T3', on the other hand, was significant in thyroids from both iodine-deficient and iodine-sufficient rats. Similarly, in thyroglobulin iodinated in vitro with thyroid peroxidase to varying levels of iodination, the formation of T2 was evident only at lower levels of iodination, whereas the formation of T3' was significant at all levels of iodination. The comparison of relative T3' and T4 formation in enzymatically iodinated thyroglobulin with corresponding values reported for the intermolecular (DIHPPA) model for T4 formation, indicates that the peroxidase model system simulates much more closely the relative formation of T3' and T4 seen in vivo.
在本研究中观察到，用¹³¹I标记18 - 24小时的严重碘缺乏大鼠甲状腺中，标记的甲状腺素（T4）占¹³¹I总量的比例不到2%，这一数值远低于先前报道的碘缺乏大鼠的数值。这一低数值归因于两个因素：1）使用碘含量低到足以导致极度碘缺乏的饲料；2）使用能成功将T4与次要碘甲状腺原氨酸3,3'-二碘甲状腺原氨酸（T2）和3',5',3-三碘甲状腺原氨酸（反式T3；T3'）分离的纸色谱系统。在严重碘缺乏时，尽管次要碘甲状腺原氨酸的生成量较低，但相对于T4的生成量而言变得相当可观。在本研究中，标记T2的生成仅在碘缺乏时显著，且在碘缺乏最严重的大鼠中观察到最高值。在后者中，标记的一碘酪氨酸（MIT）约占甲状腺中¹³¹I总量的60%，T2生成量增加可归因于两个MIT分子之间偶联概率的增加。另一方面，标记T3'的生成在碘缺乏和碘充足大鼠的甲状腺中均显著。同样，在体外经甲状腺过氧化物酶碘化至不同碘化水平的甲状腺球蛋白中，T2的生成仅在较低碘化水平时明显，而T3'的生成在所有碘化水平时均显著。将酶促碘化甲状腺球蛋白中T3'和T4的相对生成与报道的T4生成分子间（DIHPPA）模型的相应值进行比较，表明过氧化物酶模型系统更紧密地模拟了体内所见的T3'和T4的相对生成情况。
