甲状腺功能低下对大鼠肝细胞核T3受体的影响

目的探讨甲低大鼠肝核Ｔ３受体特性的变化，为阐明甲状腺激素对肝细胞核Ｔ３受体的作用提供实验资料。方法用０．５％ＮａＣｌＯ４诱导大鼠甲状腺功能低下，采用该室建立起来的Ｔ３和离体肝细胞核结合实验的方法，观察甲状腺功能低下对大鼠肝核Ｔ３受体的影响。结果甲状腺功能低下大鼠肝核Ｔ３受体的亲合常数（Ｋａ）增加，最大结合容量（ＭＢＣ）明显下降，Ｔ３受体占位率与对照组无显著差别，且ＭＢＣ与血清Ｔ３、Ｔ４呈正相关。结论肝核Ｔ３受体的数目受甲状腺激素的调节与控制，甲状腺激素对肝脏的作用主要通过调节核Ｔ３受体的结合容量，而非通过改变受体占位率来实现的

Effects of hypothyroidism on liver nuclear T3 receptors

Objective To study the changes in character of liver nuclear T 3 receptors in hypothyroid rats and give experimental evidences to illustrate the effects of thyroid hormone on the liver nuclear T 3 receptors. Methods Hypothyroid function of rats was induced by a five week treatment with NaClO 4 and changes in the liver nuclear T 3 receptors were observed by the method of T 3 binding to isolated liver cell nuclei.Results The affinity constant (Ka) of liver nuclear T 3 receptors increases in the hypothyroid rats whereas the maximal binding capacity (MBC) decreases,and the decreases of MBC was directly related to serum T 3,T 4 concentration.It is in the hypothyroid rats that the occupancy of T 3 receptors does not change.Conclusions The numbers of nuclear T 3 receptors is under control of the thyroid hormone,and thyroid hormone acts by regulating the MBC of nuclear T 3 receptors instead of by altering the occupancy of receptors.