【摘要】 大白鼠屈跖肌可因协同肌切除而引起代偿性肥大,本文以这一实验模式研究了在肌肉肥大的发展过程中,蛋白质合成速度与肌纤维成份的变化。屈跖肌的重量在手术切除腓肠肌后的第2,5、15和50天时分别增加了11、33.33和104%。肌组织蛋白的合成速度在早期未发现有变化,肌球蛋白的合成速度甚至有所降低,但在第15天与50天时,肌组织蛋白合成速度分别提高了31%和150%,肌球蛋白合成速度也分别提高了48%和52%。蛋白质在肌肉中的总含量在此期间亦相应增加。屈跖肌中慢收缩肌纤维所占比例从正常情况下的10%,提高到25%左右。以上观察表明,在骨髂肌代偿性肥大的发展过程中,蛋白质合成速度的提高是肌肉中蛋白质积累与肌纤维类型转化的主要因素,这一适应性变化过程在负荷后15天才开始明显表现出来,50天后已达到新的稳定阶段。更多还原

【Abstract】 Compensatory hypertrophy of rat plantaris muscle was induced by a total resection of the gastrocnemius, and the contralateral leg was sham-operated to serve as the control. Total tissue protein and myosin protein were extracted and their synthetic rate was estimated from [~3H] phenylalanine incorporation with the correction of intracellular amino acid availability. The results showed that the overloaded rat plantaris muscle was hypertrophic as compared with its contralateral control. The wet tissue weight increased 11, 33, 33 and 104% on the 2nd, 5th, 15th, and 50th day after operation respectively, but showed no further change of weight on the 150th day. Total muscle protein synthesis expressed as nanomoles of phenylalanine incorporated per mg of protein per hour of perfusion was unchanged during the early transition phase (2-5 days post-operative) but was significantly elevated afterwards, i.e., 31 and 150% after 15 and 50 days of chronic overload. Myosin protein synthesis was decreased in the early phase (2 days post-operative) but was significantly increased by 48 and 52% on the 15th and 50th day after operation. Histochemically, slow twitch fibers shifted from approxi mately 10% in the normal plantaris to about 25% in the overload muscle 50 days after operation, and remained elevated for at least 150 days. These data suggest that during compensatory hypertrophy, enhanced rate of protein synthesis may be the dominant mechanism for the accumulation of muscle protein and plays an important role in the transition of muscle fiber from fast to slow twitch type. However, the contribution of protein synthesis to muscle growth does not become evident until about 15 days after the initial stimulation. Although our data cannot explain the elevated protein synthesis when the muscle had appeared to achieve a steady state after 50 days workload, the possibility exists that the change in fiber composition of these muscles could account for the increased protein synthesis.更多还原