Kensler R W, Peterson S, Norberg M
Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri at Kansas City 64108.
J Muscle Res Cell Motil. 1994 Feb;15(1):69-79. doi: 10.1007/BF00123834.
Although the skeletal muscles of different vertebrate species have been assumed to be generally similar, recent X-ray diffraction and mechanical studies have demonstrated differences in the responses of these muscles to changes in physiological conditions. X-ray diffraction studies have indicated that lowering the temperature and lowering ionic strength may affect the crossbridge arrangement of rabbit thick filaments. Similar X-ray diffraction studies on the structural effects of lowering ionic strength in frog and fish muscles are less clear in interpretation, while lowering the temperature appears to have little effect in these muscles. In the present study we have compared the effects of lowering the temperature or ionic strength on the crossbridge order of isolated rabbit and fish thick filaments as observed in the electron microscope. In agreement with the X-ray results, rabbit filaments show a distinct loss of crossbridge order when stained at 4 degrees C compared to 25 degrees C, whereas fish thick filaments appear similar at both temperatures. Rabbit thick filaments, when diluted to one-fourth of the normal ionic strength (while maintaining constant EGTA and ATP concentration), showed a strong tendency to bind to actin filaments, while similarly-treated fish filaments showed little tendency to aggregate or become disordered. These results appear to support the X-ray diffraction results of other investigators, and the idea that effects of ionic strength or temperature on muscle may vary with species.
尽管不同脊椎动物物种的骨骼肌通常被认为是相似的，但最近的X射线衍射和力学研究表明，这些肌肉对生理条件变化的反应存在差异。X射线衍射研究表明，降低温度和降低离子强度可能会影响兔粗肌丝的横桥排列。关于降低青蛙和鱼类肌肉离子强度的结构效应的类似X射线衍射研究，其解释不太明确，而降低温度在这些肌肉中似乎影响不大。在本研究中，我们比较了降低温度或离子强度对电子显微镜下观察到的分离兔和鱼粗肌丝横桥排列的影响。与X射线结果一致，与25℃相比，兔肌丝在4℃染色时横桥排列明显丧失，而鱼粗肌丝在两个温度下看起来相似。兔粗肌丝在稀释至正常离子强度的四分之一时（同时保持EGTA和ATP浓度恒定），表现出强烈的与肌动蛋白丝结合的倾向，而经过类似处理的鱼肌丝几乎没有聚集或变得无序的倾向。这些结果似乎支持了其他研究者的X射线衍射结果，以及离子强度或温度对肌肉的影响可能因物种而异的观点。
