Sharma R, Timiras P S
Biochim Biophys Acta. 1987 Sep 14;930(2):237-43. doi: 10.1016/0167-4889(87)90036-x.
Specific binding of [3H]dexamethasone to cytosol and the activation of bound hormone-receptor complexes were studied in the liver of immature (3 weeks old) and mature (26 weeks old) Long-Evans male rats. The concentration of specific binding sites was significantly higher (33%) in the liver of immature rats as compared to mature, while dissociation constants (Kd) remain unaltered at both ages. Heat activation (for 45 min at 25 degrees C) significantly enhances the binding of [3H]dexamethasone-receptor complexes to DNA-cellulose and purified nuclei at both the ages, with a greater magnitude in mature rats. Cross mixing experiments (i.e., binding of activated cytosol from mature rats to nuclei of immature and vice-versa) show receptor specificity. Ca2+ activation (20 mM Ca2+ for 45 min at 0 degree C) also enhances the nuclear and DNA-cellulose binding at both the ages, but to a similar extent. Differences in the number of specific binding sites and some of the physiochemical properties of glucocorticoid receptors presented here between immature and mature rats may underlie the functional changes in tissue response with age.
在未成熟（3周龄）和成熟（26周龄）的Long-Evans雄性大鼠肝脏中，研究了[3H]地塞米松与胞质溶胶的特异性结合以及结合的激素-受体复合物的活化情况。与成熟大鼠相比，未成熟大鼠肝脏中特异性结合位点的浓度显著更高（33%），而两个年龄段的解离常数（Kd）保持不变。热激活（在25℃下45分钟）显著增强了两个年龄段的[3H]地塞米松-受体复合物与DNA-纤维素和纯化细胞核的结合，在成熟大鼠中的增强幅度更大。交叉混合实验（即将成熟大鼠的活化胞质溶胶与未成熟大鼠的细胞核结合，反之亦然）显示了受体特异性。Ca2+激活（在0℃下20 mM Ca2+处理45分钟）也增强了两个年龄段的细胞核和DNA-纤维素结合，但程度相似。此处呈现的未成熟和成熟大鼠之间糖皮质激素受体特异性结合位点数量以及一些理化性质的差异，可能是组织反应随年龄发生功能变化的基础。
