Svec F, Rudis M
Endocrinology. 1982 Aug;111(2):699-702. doi: 10.1210/endo-111-2-699.
After 5 days of incubation with 10 nM tritiated dexamethasone, the amount of glucocorticoid displaceably-bound by the ACTH-secreting, glucocorticoid-responsive AtT-20 mouse pituitary tumor cell decreases by 70-80%. This decrease takes place in both the cytosolic and nuclear fractions. Although one might predict that there should be a decrease in agonist efficacy associated with this loss of nuclear binding, there was not; long-term incubations with dexamethasone revealed that the AtT-20 cells showed no tendency to resume secreting ACTH. Hence, although there was a dramatic decrease in the amount of nuclear-bound steroid, there was not a resulting decrease in the steroid's biopotency. These results suggest that the agonist-induced decrease in receptor content is either a means of removing redundant nuclear receptors, or a new, previously unrecognized, step in the mechanism of glucocorticoid hormone action.
在用10纳摩尔氚标记的地塞米松孵育5天后，促肾上腺皮质激素分泌型、糖皮质激素反应性AtT-20小鼠垂体肿瘤细胞中可被置换结合的糖皮质激素量减少了70 - 80%。这种减少在胞质和核组分中均有发生。尽管有人可能预测，随着核结合的丧失，激动剂效力应该会降低，但实际并非如此；用地塞米松进行长期孵育显示，AtT-20细胞没有恢复分泌促肾上腺皮质激素的趋势。因此，尽管核结合类固醇的量显著减少，但类固醇的生物活性并没有随之降低。这些结果表明，激动剂诱导的受体含量减少要么是去除多余核受体的一种方式，要么是糖皮质激素作用机制中一个新的、以前未被认识到的步骤。
