Pregelj Peter, Sketelj Janez
Institute of Pathophysiology, School of Medicine, University of Ljubljana, Ljubljana, Slovenia.
J Neurosci Res. 2002 Jan 1;67(1):114-21. doi: 10.1002/jnr.3000.
Slow antigravity muscles differ from fast muscles with regard to load bearing performed during contraction. We examined the importance of load bearing in regulation of acetylcholinesterase (AChE) expression in slow and fast rat muscles. The levels of AChE mRNA in the slow soleus muscles are about 30% of those in the fast extensor digitorum longus (EDL) muscles. In the soleus muscles unloaded for 8 days by hindlimb suspension, AChE mRNA levels were not significantly different from those in the control soleus muscles. In the suspended animals, AChE transcripts in the EDL muscles decreased to about 80% of control levels. Reduction of the resting muscle tension by joint fixation did not significantly affect the levels of AChE mRNA in the unloaded soleus muscles. Phasic high-frequency electrical stimulation of the unloaded soleus muscles via the sciatic nerve increased their AChE mRNA levels to about 50% of those in the EDL muscles. The levels observed after phasic stimulation were significantly higher than those after low-frequency tonic stimulation, indicating the importance of muscle activation pattern for AChE regulation also in the absence of load bearing. The AChE mRNA levels in the soleus muscles overloaded for 8 days by synergist muscle ablation increased significantly to about 50% of those in the EDL muscle. The load bearing during muscle contraction seems to be a relatively unimportant extrinsic factor in the regulation of the AChE mRNA levels in muscle fibers, except when an increased load induces muscle hypertrophy accompanied by the fusion of satellite cells with the muscle fibers.
慢抗重力肌在收缩过程中承受的负荷与快肌不同。我们研究了负荷在调节大鼠慢肌和快肌中乙酰胆碱酯酶（AChE）表达方面的重要性。慢比目鱼肌中AChE mRNA的水平约为快趾长伸肌（EDL）中水平的30%。通过后肢悬吊使比目鱼肌卸载8天，其AChE mRNA水平与对照比目鱼肌相比无显著差异。在悬吊的动物中，EDL肌中的AChE转录本降至对照水平的约80%。通过关节固定降低静息肌张力，对卸载的比目鱼肌中AChE mRNA水平没有显著影响。通过坐骨神经对卸载的比目鱼肌进行阶段性高频电刺激，可使其AChE mRNA水平增加至EDL肌中水平的约50%。阶段性刺激后观察到的水平显著高于低频强直刺激后的水平，这表明在无负荷情况下，肌肉激活模式对AChE调节也很重要。通过协同肌切除使比目鱼肌过载8天，其AChE mRNA水平显著增加至EDL肌中水平的约50%。肌肉收缩过程中的负荷似乎是调节肌纤维中AChE mRNA水平相对不重要的外在因素，除非增加的负荷诱导肌肉肥大并伴有卫星细胞与肌纤维融合。
