【摘要】 目的:通过对大鼠外源性注射IGF-I及LY294002,结合运动训练,观察骨骼肌mTOR及其下游信号在IGF-I和运动介导骨骼肌蛋白质合成中的作用。方法:雄性成年SD大鼠随机分为8组:安静组(S)、IGF-I组(SI)、阻断剂组(SL)、IGF-I+阻断剂组(SIL),运动组(E)、运动+IGF-I组(EI)、运动+阻断剂组(EL)和运动+IGF-I+阻断剂组(EIL)。对大鼠进行1周的跑台训练(20m/min,10%,60min/d)。每天训练后即刻对SL、SIL、EL、EIL组腹腔注射LY294002,对SI、SIL、EI、EIL组小腿内侧皮下注射IGF-I。最后一次训练后6小时取注射侧腿腓肠肌,用Bradford法测试肌肉总蛋白浓度,用Western Blot法测定骨骼肌mTOR(Ser 2448)、p70S6K(Thr389)和4EBP1(Thr37/46)蛋白磷酸化表达。结果:(1)1周外源性注射LY294002抑制了mTOR及其下游信号,使各信号蛋白表达水平显著降低。(2)1周注射IGF-I使mTOR及其下游信号表达水平显著升高。(3)1周耐力运动增加了mTOR及其下游信号表达水平。(4)运动和IGF-I共同作用使大鼠mTOR及其下游信号的表达水平明显高于单纯运动或单独注射IGF-I。结论:(1)外源性IGF-I对mTOR及其下游信号具有强激活效应,这可能是IGF-I介导骨骼肌蛋白质合成的重要机制之一。(2)LY294002对mTOR及其下游信号有阻断效应,且运动、IGF-I可以在一定程度上对抗LY294002对mTOR及其下游信号的阻断效应。更多还原

【Abstract】 Object:To study the effect and regulating mechanism of mTOR and downstream of mTOR on protein synthesis in skeletal muscle which is stimulated by IGF-I. methods:Male adult SD rats were randomly divided to eight groups;sedentary group(S),sedentary and IGF-I group(SI),blocker group(SL),sedentary and IGF-I plus LY294002 injection group(SIL),exercise group(E),exercise and LY294002 injection group(EIL).After all the groups had been adapted for one week,the rats of four exercise groups performed closely monitored formal training in treadmills(20m/mm at 10% slope,60 min;once per day) for one week.All the injection groups were injected at the same time immediately after exercise every day.After the 7days of normal training,the gastrocnemius muscle of the injection side was collected at 6th hour post exercise.Protein content of gastrocnemius muscle was assessed with Bradford.Phosphorylation of mTOR(Ser2448),p70S6K(Thr389) and 4EBP1(Thr37/46) were measured by Western Blot. Results:(1) One-week LY294002 injection inhibited the phosphorylation of mTOR(Ser2448),p70S6K(Thr389) and 4EBP1(Thr37/46).(2) One week exogenous IGF-I injection promoted the phosphorylation of mTOR(Ser2448),p70S6K(Thr389) and 4EBP1(Thr37/46) significantly.(3) One week endurance exercise increased the Phosphorylation of mTOR(Ser2448),p70S6K(Thr389) and 4EBP1(Thr37/46).(4) Exercise plus IGF-I injection has higher level of mTOR and downstreams of mTOR than exercise or IGF-I respectively. Conclusion:(1) Eexogenous IGF-I is a potent activator of muscle growth and appears to mediate this effect through the activation of the mTOR and downstreams of mTOR.(2) LY294002 can significantly suppress the activation of mTOR and downstreams of mTOR,and both exercise and IGF-I can attenuated the inhibition effect of LY294002.(3) Exercise and IGF-I injection have an accumulative effect on the activation of mTOR and downstreams of mTOR.更多还原