Goodman C A, Stephenson G M
Muscle Cell Biochemistry Laboratory, School of Life Sciences and Technology, Victoria University, Melbourne, Australia.
J Muscle Res Cell Motil. 2000;21(7):655-62. doi: 10.1023/a:1005628500892.
There is increasing evidence that endogenous glycogen depletion may affect excitation-contraction (E-C) coupling events in vertebrate skeletal muscle. One approach employed in physiological investigations of E-C coupling involves the use of mechanically skinned, single fibre preparations obtained from tissues stored under paraffin oil, at room temperature (RT: 20-24 degrees C) and 4 degrees C for several hours. In the present study, we examined the effect of these storage conditions on the glycogen content in three muscles frequently used in research on E-C coupling: rat extensor digitorum longus (EDL) and soleus (SOL) and toad iliofibularis (IF). Glycogen content was determined fluorometrically in homogenates prepared from whole muscles, stored under paraffin oil for up to 6 h at RT or 4 degrees C. Control muscles and muscles stored for 0.5 and 6 h were also analysed for total phosphorylase (Phos(total)) and phosphorylase a (Phos a) activities. No significant change was observed in the glycogen content of EDL and SOL muscles stored at RT for 0.5 h. In rat muscles stored at RT for longer than 0.5 h, the glycogen content decreased to 67.6% (EDL) and 78.7% (SOL) of controls after 3 h and 25.3% (EDL) and 37.4% (SOL) after 6 h. Rat muscles stored at 4 degrees C retained 79.0% (EDL) and 92.5% (SOL) of glycogen after 3 h and 75.2% (EDL) and 61.1% (SOL) after 6 h. The glycogen content of IF muscles stored at RT or 4 degrees C for 6 h was not significantly different from controls. Phos(total) was unchanged in all muscles over the 6 h period, at both temperatures. Phos a was also unchanged in the toad IF muscles, but in rat muscles it decreased rapidly, particularly in EDL (4.1-fold after 0.5 h at RT). Taken together these results indicate that storage under paraffin oil for up to 6 h at RT or 4 degrees C is accompanied by minimal glycogen loss in toad IF muscles and by a time- and temperature-dependent glycogen loss in EDL and SOL muscles of the rat.
越来越多的证据表明，内源性糖原耗竭可能会影响脊椎动物骨骼肌中的兴奋 - 收缩（E - C）偶联事件。在E - C偶联的生理学研究中采用的一种方法涉及使用从在室温（RT：20 - 24摄氏度）和4摄氏度下保存在石蜡油中的组织中获得的机械去表皮单纤维制剂，保存数小时。在本研究中，我们研究了这些储存条件对E - C偶联研究中常用的三块肌肉中糖原含量的影响：大鼠趾长伸肌（EDL）、比目鱼肌（SOL）和蟾蜍髂腓肌（IF）。通过荧光法测定从整块肌肉制备的匀浆中的糖原含量，这些肌肉在RT或4摄氏度下在石蜡油中保存长达6小时。还分析了对照肌肉以及保存0.5小时和6小时的肌肉的总磷酸化酶（Phos(total)）和磷酸化酶a（Phos a）活性。在RT下保存0.5小时的EDL和SOL肌肉的糖原含量未观察到显著变化。在RT下保存超过0.5小时的大鼠肌肉中，糖原含量在3小时后降至对照的67.6%（EDL）和78.7%（SOL），在6小时后降至25.3%（EDL）和37.4%（SOL）。在4摄氏度下保存的大鼠肌肉在3小时后保留了79.0%（EDL）和92.5%（SOL）的糖原，在6小时后保留了75.2%（EDL）和61.1%（SOL）。在RT或4摄氏度下保存6小时的IF肌肉的糖原含量与对照无显著差异。在两个温度下的6小时期间，所有肌肉中的Phos(total)均未改变。蟾蜍IF肌肉中的Phos a也未改变，但在大鼠肌肉中它迅速下降，特别是在EDL中（在RT下0.5小时后下降4.1倍）。综上所述，这些结果表明，在RT或4摄氏度下在石蜡油中保存长达6小时，蟾蜍IF肌肉中的糖原损失最小，而大鼠的EDL和SOL肌肉中的糖原损失则与时间和温度有关。
