Kushmerick M J, Meyer R A, Brown T R
Adv Exp Med Biol. 1983;159:303-25. doi: 10.1007/978-1-4684-7790-0_27.
It is clear that the combination of 31P NMR studies of muscle and of other organs with biochemical and physiological measurements is an extremely powerful method for studying cellular energetics. We have presented examples of our on-going experiments. Well defined and stable in vitro preparations of mammalian fast-twitch (cat biceps) and slow-twitch (cat soleus) muscles are developed. Erythrocyte-containing perfusate is needed for adequate oxygenation during stimulation. It is not clear why fluorocarbon suspensions are inadequate. Inorganic phosphate levels in the fast-twitch biceps as determined from NRM spectra are close to lmM, that is very much lower than the value (6 mM) derived from chemical measurements of muscle extracts. A similar discrepancy in the slow-twitch soleus cannot yet be established; if it exists, the discrepancy is small. From the metabolite contents, the free energy available from ATP splitting is similar in both muscle types: -63 kJ/mole in biceps and -57 kJ/mole in soleus. Kinetic NMR measurements indicate the creatine phosphokinase reaction is at equilibrium, and in biceps the unidirectional fluxes are 5 mumole per gram per sec. Transient alkalinization of intracellular pH during stimulation periods and acidification during recovery periods are clearly seen. In the biceps the alkalinization is much smaller than in soleus, and suggests a greater buffer capacity in fast-twitch muscles. Both muscles recovery from prolonged ischemic periods upon reperfusion, although the recovery rate is very much slower than that from 10-20 min periods of stimulation in which similar decreases of PCr and increases of Pi occur. The pattern of recovery is however quite similar. Perfused muscles may be a useful model for studying ischemia, anoxia and hypoxia and are useful preparations for a wide variety of metabolic and energetic studies of fast-twitch and slow-twitch mammalian skeletal muscles.
显然，将肌肉和其他器官的31P核磁共振研究与生化和生理测量相结合，是研究细胞能量学的一种极其强大的方法。我们已经展示了我们正在进行的实验的例子。已经开发出了明确且稳定的哺乳动物快肌（猫二头肌）和慢肌（猫比目鱼肌）的体外制剂。在刺激过程中，需要含红细胞的灌注液以实现充分的氧合。目前尚不清楚为什么氟碳悬浮液不充分。从核磁共振光谱确定的快肌二头肌中的无机磷酸盐水平接近1毫摩尔，这比从肌肉提取物的化学测量得出的值（6毫摩尔）低得多。慢肌比目鱼肌中类似的差异尚未确定；如果存在，差异也很小。从代谢物含量来看，两种肌肉类型中ATP分解产生的自由能相似：二头肌中为-63千焦/摩尔，比目鱼肌中为-57千焦/摩尔。动力学核磁共振测量表明肌酸磷酸激酶反应处于平衡状态，在二头肌中单向通量为每秒每克5微摩尔。在刺激期内细胞内pH值的短暂碱化以及恢复期内的酸化都清晰可见。在二头肌中，碱化程度比在比目鱼肌中小得多，这表明快肌具有更大的缓冲能力。两种肌肉在再灌注后都能从长时间的缺血期恢复，尽管恢复速度比在10 - 20分钟刺激期后的恢复速度慢得多，在10 - 20分钟刺激期内会出现类似的磷酸肌酸减少和无机磷酸盐增加的情况。然而，恢复模式非常相似。灌注肌肉可能是研究缺血、缺氧和低氧的有用模型，并且是用于快肌和慢肌哺乳动物骨骼肌的各种代谢和能量研究的有用制剂。
