甲状腺激素对心肌β肾上腺素受体更新速率的影响

The Effect of Thyroid Hormones on the Turnover of Cardiac β-adrenoreceptors

受体放射配基结合实验证明,BAlpM一次腹腔注射使心肌β受体约65～75％被不可逆地阻断,随后逐渐上升。根据受体数恢复的时相曲线,用一定数学模型可算出心肌β受体的代谢动力学参数生成速率Pr及降解速率常数Kd。用Balb/c青年小鼠测得正常Pr值为0.14fmol·mg蛋白—1·h—1,Kd为0.0074/h,半更新时间平均为96小时。给青年Balb/c小鼠注射T_3造成甲高模型,Pr增加104％,Kd增加52％,故实验结果表明,甲状腺激素同时促进心肌β受体的生成和降解,但生成的加快明显超过降解的加快,结果使受体的结合位点数升高到一个新的稳定水平。

125I-Pindolol binding assay revealed that BAlpM, either applied to the assay system in vitro ot applied in vivo before taking the tissues, is a strong irreversible blocker of lung and heart β-adreno|eceptors, after a single for intraperitoneal injection of BAlpM 4 hours, heart β-adienoreceptor density droppped to a minimum value which was about 65-75% of the steady state Rmax. After then,the density rose gradually and restored to original Rmax at about 240 hours after the injection. Mathematical models were derived to compute the production rate (Pr) and degradation rate constant (Kd) from the time course curve. For young Balb/c mice, normal value for Pr and Kd were to be 0.14 fmol/mg determinated protein and 0.0074/h respectively.s In hyperthyroid models produced by injections of T3, Pr was increased by 104% and Kd was increased by 52%,both were significantly higher than normal. It is concluded that thyroid hormones promote both that of the production and the degradation of heart β-adrenoreceptors, with a prevalence on the production rate which should in turn lead to a higher stready level of the β-adrenorec eptor density.