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目的通过观察1周注射外源性胰岛素样生长样子(IGF-Ⅰ)和跑台运动对mTOR及其上游信号的影响,以深入探讨IGF-Ⅰ对运动骨骼肌蛋白合成信号的影响机理。方法 8周龄雄性SD大鼠在适应性训练后分为4组:安静组(S)、IGF-Ⅰ组(SI)、运动组(E)、运动+IGF-Ⅰ组(EI),每组6只。运动方式为跑台运动(坡度为10%,跑速20m/min,60 min),每天1次,共7 d。外源性IGF-Ⅰ为小腿后侧肌肉隆起处的皮下注射。用Western Blotting法检测腓肠肌MHC、PI3K蛋白、Akt(Ser473)和mTOR(Ser2448)磷酸化表达。结果 1周后,外源性IGF-Ⅰ显著促进骨骼肌湿重和MHC的表达,骨骼肌PI3K蛋白和Akt(Ser473)、mTOR(Ser2448)的磷酸化表达显著增加。运动显著促进Akt(Ser473)和mTOR(Ser 2448)磷酸化的表达。结论 (1)1周外源性IGF-Ⅰ注射明显促进骨骼肌蛋白合成,且明显强于运动的促合成效应;(2)1周外源性IGF-Ⅰ注射明显促进运动骨骼肌mTOR及其上游信号的活性,运动与IGF-Ⅰ具有协同效应,共同促进骨骼肌肥大。
Objective To investigate the effect of IGF-Ⅰ on the signal of mTOR and its upstream signal by observing the effect of IGF-Ⅰ and treadmill exercise in one week. Methods Eight-week-old male Sprague-Dawley rats were randomly divided into 4 groups: sedentary group, SI group, exercise group, exercise + IGF-Ⅰ group, 6 only. Exercise for the treadmill exercise (gradient 10%, running speed 20m / min, 60 min), 1 day, a total of 7 d. Exogenous IGF-I is injected subcutaneously at the muscular uplift of the calf. Western Blotting was used to detect the phosphorylation of MHC, PI3K, Akt (Ser473) and mTOR (Ser2448) in gastrocnemius muscle. Results After 1 week, the exogenous IGF-Ⅰ significantly promoted the skeletal muscle wet weight and MHC expression. The phosphorylation of skeletal muscle PI3K, Akt (Ser473) and mTOR (Ser2448) increased significantly. Exercise significantly promoted the phosphorylation of Akt (Ser473) and mTOR (Ser 2448). Conclusions (1) Exogenous IGF-Ⅰ injection for one week significantly stimulates the synthesis of skeletal muscle protein and is significantly stronger than the pro-acting effect of exercise. (2) The exogenous IGF-Ⅰ injection for one week obviously stimulates the activity of mTOR and its upstream signal in exercise skeletal muscle , Exercise and IGF-Ⅰ have a synergistic effect, together to promote skeletal muscle hypertrophy.