运动过程中糖皮质激素受体减少的机制探讨——GR mRNA的变化

同步观察大鼠在 7周递增负荷训练过程中血浆皮质酮、肝胞液糖皮质激素受体 (GR)和肝脏GRmRNA的动态变化 ,试图从GRmRNA水平上探讨运动应激后GR变化的机制。SD大鼠随机分为对照组 ,训练 3周组 ,训练 5周组 ,训练 7周组 ,训练 7周 +恢复 1周组。动物训练采用递增负荷的跑台训练。采用放射配体结合分析法测定肝胞液GR结合量 ;定量RT -PCR检测肝GRmRNA表达。结果发现 :(1) 7周递增负荷训练过程中 ,血浆皮质酮浓度表现为不断增加 ,至第 7周达最高 ,第 8周 (恢复周 )又降至接近对照组水平。 (2 )大鼠在 7周递增负荷训练过程中 ,肝胞液GR呈持续下降 ,至训练第 7周降至最低 ,恢复 1周后大鼠肝胞液GR有回升。 (3)在 7周递增负荷训练过程中 ,肝脏GRmRNA的变化与肝胞液GR的变化相近 ,与肝胞液GR的变化不同 ,恢复 1周后肝GRmRNA已恢复至正常水平。结果表明 ,递增运动负荷训练过程中GR结合容量的减少至少部分地发生在mRNA水平上 ,即由于GRmRNA的减少 ,造成GR分子的合成减少。但是 ,GR结合容量的恢复速度比GRmRNA慢 ,提示训练过程中 ,大鼠肝GR结合容量的减少不全是GRmRNA减少的结果 ,可能还有其他影响因素 ,比如GR结合活性的减少和 /或GR蛋白分解加速。

Study of the Mechanism of the Decrease in Glucocorticoid Receptor during Physical Training——Changes of the GR mRNA

In this paper, we explored the mechanism of the GR reduction during exercise training by analyzing the interrelationship between reduction of glucocorticoid binding capacity and induction of GR mRNA. SD rats were randomly divided in five groups: (1) control, (2) training for 3 weeks, (3) training for 5 weeks, (4) training for 7 weeks and (5) training for 7 weeks and rest for 1 week. The rats were trained in a progressive increasing training load manner. GR mRNA expression was detected by RT-PCR and glucocorticoid binding capacity in hepatic cytosol was measured by radioligand binding assay. The results were as follows: the plasma concentrations of corticosterone increased progressively during incremental loading and fell to the control level after stopping training for one week; both hepatic cytosol GR and GR-mRNA in rats decreased during incremental loading even though dynamic differences existed. These results indicated that the decrease of hepatic GR after training occurs partially at mRNA levels and other mechanisms such as the possibilities of the decrease in hormone binding activity of GR and the increase of GR protein decomposition may be also involved.