du Breuil A, Galton V A
Acta Endocrinol (Copenh). 1978 May;88(1):87-93. doi: 10.1530/acta.0.0880087.
The importance of the monodeiodination of T4 to T3 in the physiological action of T4 was explored by assessing the role of T4 in maintaining prophylthiouracil (PTU)-treated rats during exposure to 4 degrees C. (PTU inhibits both thyroid hormone biosynthesis and T4 to T3 conversion in peripheral tissues.) Firstly, the effects of cold exposure on the metabolism of T4 in control and PTU-treated rats equilibrated with [125I]T4 (2 microgram/100 g b. w./day) were determined. PTU was administered in the food (2 mg/g food). In control rats, no significant changes in T4 metabolism occurred during 3 days at 4 degrees C. Urinary 125I was greatly decreased in PTU-treated rats. Exposure of these rats to cold resulted in some increase but values were still 50% below normal. Secondly, four groups of rats were exposed to cold: control; PTU-treated; T4-treated; PTU + T4-treated. Control and T4-treated rats survived. PTU-treated rats died unless T4 was administered. Radioimmunoassay of T4 and T3 indicated significant concentrations of T3 in sera of rats from all but the PTU + T4 group. These results suggest that T4 permits survival in the cold-exposed PTU-treated rat without being converted to T3 and thus they support the concept that T4 has intrinsic biological activity.
通过评估甲状腺素（T4）在维持丙硫氧嘧啶（PTU）处理的大鼠暴露于4℃环境时的作用，探讨了T4单碘脱碘转化为三碘甲状腺原氨酸（T3）在T4生理作用中的重要性。（PTU可抑制甲状腺激素的生物合成以及外周组织中T4向T3的转化。）首先，测定了冷暴露对用[125I]T4（2微克/100克体重/天）平衡的对照大鼠和PTU处理大鼠中T4代谢的影响。PTU以2毫克/克食物的剂量掺入食物中。在对照大鼠中，4℃环境下3天内T4代谢未发生显著变化。PTU处理的大鼠尿中125I显著减少。这些大鼠暴露于寒冷环境后有所增加，但仍比正常水平低50%。其次，将四组大鼠暴露于寒冷环境：对照组；PTU处理组；T4处理组；PTU + T4处理组。对照和T4处理的大鼠存活。PTU处理的大鼠除非给予T4否则会死亡。对T4和T3的放射免疫分析表明，除PTU + T4组外，所有组大鼠血清中T3均有显著浓度。这些结果表明，T4可使暴露于寒冷环境的PTU处理大鼠存活，而无需转化为T3，因此支持了T4具有内在生物活性这一概念。
