Zucchelli G C, Pilo A, Giannessi D, Bianchi R, Cazzuola F, Molea N
Metabolism. 1980 Oct;29(11):1031-6. doi: 10.1016/0026-0495(80)90212-7.
The appearance in human serum of labeled iodothyronines arising from 3,5,3'-triiodothyronine (T3) catabolism was measured after bolus administration of 125I-T3. The use of column chromatography made it possible to separate in the plasma samples iodoproteins, iodide, T3 and a fourth peak ("pre-T3") eluting just before T3. The radioactivity associated with this pre-T3 peak was found to be 0.5% of T3 activity 30 min after injection, and reached a plateau value of 5.6% +/- 1.2 (mean +/- SD) from the 10th hr onward. From these data, we calculated that a maximal 5% underestimation in T3 metabolic clearance rate is inherent in those analytical methods that do not completely separate pre-T3 from T3 radioactivity. The MCR of 3,3'-diiodothyronine (T2) was also measured from the plasma disappearance curve after single injection of 125I-3,3'-T2. From these data and the mean disappearance curve of T3, the appearance curve of 3,3'-T2 in plasma was reconstructed by convolution under the assumption of a 100% conversion of T3 to 3,3'-T2. A plateau value of 4.6% of T3 activity was computed, very comparable to the experimentally determined 5.6%. This suggest that, if labeled 3,3'-T2 is the main component of the pre-T3 peak, the conversion into 3,3'-T2 represents a major pathway of T3 metabolism in man.
在静脉注射125I-T3后，测定了由3,5,3'-三碘甲状腺原氨酸（T3）分解代谢产生的标记碘甲状腺原氨酸在人血清中的出现情况。使用柱色谱法能够在血浆样本中分离出碘蛋白、碘化物、T3以及在T3之前洗脱的第四个峰（“前T3”）。发现与该前T3峰相关的放射性在注射后30分钟时为T3活性的0.5%，并从第10小时起达到5.6%±1.2（平均值±标准差）的平稳值。根据这些数据，我们计算出在那些不能将前T3与T3放射性完全分离的分析方法中，T3代谢清除率最大会有5%的低估。在单次注射125I-3,3'-二碘甲状腺原氨酸（T2）后，还从血浆消失曲线测定了3,3'-二碘甲状腺原氨酸（T2）的代谢清除率。根据这些数据以及T3的平均消失曲线，在假设T3完全转化为3,3'-T2的情况下，通过卷积重建了血浆中3,3'-T2的出现曲线。计算出的平稳值为T3活性的4.6%，与实验测定的5.6%非常接近。这表明，如果标记的3,3'-T2是前T3峰的主要成分，那么转化为3,3'-T2代表了人类T3代谢的主要途径。
