Nisula B C, Galton V A, Ingbar S H
Endocrinology. 1977 May;100(5):1432-6. doi: 10.1210/endo-100-5-1432.
A new method for assessing thyroxine (T4) metabolism in the rat has been devised and the results that it yields have been compared to those obtained by other methods for assessing peripheral T4 metabolism. The new method uses a simple analysis of the kinetics of exogenous T4 metabolism in rats chronically treated with daily injections of exogenous labeled T4 to determine T4 clearance rates via both fecal and deiodinative pathways. Fecal clearance rates of endogenously labeled hormone measured in rats brought into approximate 125I/127I specific activity equilibrium by administration of iodide of know specific activity in the drinking water were nearly the same as those determined with this new method. Furthermore, total T4 clearance rate determined with the new method agreed well with that measured by the standard single injected technique utilizing radioactive T4. These results indicate that quantitation of the clearance rate of endogenous T4 via not only the fecal, but also the deiodinative, pathway for T4 disposal can be achieved with this new method. In rats made hyperthyroid with exogenous T4, clearance rates of T4 via both deiodinative and fecal pathways were markedly increased. This result supports the concept that hyperthyroidism increases the activity of the tissue mechanisms for metabolizing T4.
已设计出一种评估大鼠甲状腺素（T4）代谢的新方法，并将其所得结果与通过其他评估外周T4代谢的方法所获得的结果进行了比较。该新方法通过对长期每日注射外源性标记T4的大鼠中外源性T4代谢动力学进行简单分析，来确定经粪便和脱碘途径的T4清除率。通过在饮用水中给予已知比活度的碘化物，使大鼠体内内源性标记激素的125I/127I比活度达到近似平衡，所测得的内源性标记激素的粪便清除率与用这种新方法测定的结果几乎相同。此外，用新方法测定的总T4清除率与利用放射性T4的标准单次注射技术所测得的结果吻合良好。这些结果表明，用这种新方法不仅可以定量内源性T4经粪便途径，还可以定量经脱碘途径的T4清除率。在用外源性T4使大鼠发生甲状腺功能亢进时，T4经脱碘和粪便途径的清除率均显著增加。这一结果支持了甲状腺功能亢进会增加组织代谢T4机制活性的观点。
