【摘要】 以M受体选择性烷化剂BCM将小鼠脑内原有M受体不可逆地阻断,用3H- QNB测定新生受体的时相曲线,通过数学模型求解生成和降解速率。平行实验表 明,甲减小鼠脑M受体增多,但更新慢于正常动物,两组半更新时间(h)分别为 26.96±1.26和19.47±1.15,降解速率常数(=更新速率常数,1/h)为 0.0257± 0.0012和0.0356±0.0021(P<0.001),受体生成速率无明显差异,故甲状腺激素 对M受体的更新有调节作用,甲减时脑M受体增多主要由于降解变慢。 甲减小鼠用助阳药附子肉桂后,脑M受体的更新速率常数平均比甲减组增加 117％(P<0.01)。甲减用附桂组的受体生成速率也有升高趋势,但不如更新速率 常数的升高幅度大,故结果表明,附子肉桂使脑M受体数降低的机制,在于同时促 进甲减动物脑M受体的生成和降解,但更新速率常数的加快占优势,结果使异常升 高的脑M受体数降低。更多还原

【Abstract】 A single injection of 25mg/kg of BCM results in irreversible block (alkylation)of about 90% of M-receptors and the time course of RT values of brain M-receptors was determined by the single-point binding assay with 3H-QNB. The production rate(Pr)and turnover rate constant(K)were calculated with a computer program from the time course of RT vaiues.Parallel experiments showed that the steady level of brain M-receptor RT without BCM treatment was signifcantly higher but the turnover rate was significantly slower in hypothyroid mice than in normal mice.The average half-lives(h) were 26.96±1.26 and 19.47±1.15 and the average turnover rate constans(l/h)were 0.0257±0.0012 and 0.0356 ±0.0021 respectively. On the other hand, the average Pr of model mice was not significantly different from mormal. It is therefore suggested that one of the important mechanisms responsible for the increase of brain M-receptor binding sites in hypothyroidism is a slow down of the turnover of receptor molecules.Experiments with Radix Aconiti Preparata (RAP)+Cortex Cinnamomi (CC) treatment showed that the turnover rate constant of hypothyroid mice was significantly elevated by RAP+CC, with an average increase of 117%. The producton rate was also elevated by RAP+CC, but only to a minor degree. Thus the mechanism, of the action of RAP+ CC is mainly to speed up the turnover (degradation) rate constant of M-receptor molecules.更多还原