PH REGULATION IN SKELETAL MUSCLE--DESIGN & PLASTICITY

脊椎动物骨骼肌对细胞内的调节能力 PH(Phi)很少受到关注，尽管事实是 Phi的变化对肌肉收缩有显著影响 和新陈代谢。只有在两块肌肉中，青蛙半腱肌 和小鼠比目鱼肌，有膜运输系统 对pH调节的责任进行了描述。在建议的 研究，将解决三个问题，目的是 更全面地定义肌肉细胞功能之间的关系 和phi调节。I)是青蛙体内的pH调节系统 肌肉(Na/H和(Na+HCO3)/C1交换器)定位于 表面膜、T管膜还是两者兼而有之？ 将通过研究实现转运体的本地化：PH (用玻璃电极)恢复甘油休克纤维(其T 小管泡化，不再与外部接触 介质)；表面形成的大小泡的pH恢复 膜；钠摄取到由以下两种物质制成的小囊泡中 表面或T管膜；以及酸挤压到T中 管腔，使用不透水的pH敏感荧光染料。 二)对未搅拌的层进行酸化，特别是T管 流明，限制phi恢复的速度和程度？的影响 未搅拌的层数将通过单次测量回收率进行评估 与多细胞制剂和暴露在不同环境中的纤维相比 外部缓冲浓度。挤压酸液对玉米生长发育的影响 未搅拌层的酸碱值将直接用pH- 靠近纤维表面的敏感电极，使用pH- T管腔内有敏感的荧光染料。三)如何 红色肌肉纤维和白色肌肉纤维调节pH值的能力不同？ 缓冲能力、PHI恢复的速度和程度以及 负责恢复的运输系统的属性将 在小鼠比目鱼肌(红色)和EDL(白色)肌肉中进行比较。 这些研究将代表着载体的第一次本地化 肌膜系统，首次直接测量pH T管腔内与pH调节的第一相关性 具有细胞代谢和收缩特性的能力。 除了对pH值调节的基本理解之外，在这些 研究，关于pH调节的详细知识可能会揭示 肌肉营养不良的病因学和/或症状 肌强直。这些疾病的主要损害之一是 膜性质的改变会导致改变 收缩和代谢过程。Phi中的角色发生变化 调控能力在此类病理中可能发挥的作用有待进一步研究 学习。

The ability of vertebrate skeletal muscle to regulate intracellular pH (pHi) has received very little attention, despite the fact that changes in pHi can have a marked effect on muscle contraction and metabolism. Only in two muscles, the frog semitendinosus and the mouse soleus, have the membrane transport systems responsible for pH regulation been described. In the proposed research, three questions will be addressed with the aim of defining more fully the relationship between muscle cell function and pHi regulation. i) Are the pH-regulating systems in frog muscle (Na/H and (Na+HCO3)/C1 exchangers) localized to the surface membrane, the T tubular membrane or both? Localization of the transporters will be achieved by studying: pH recover (with glass electrodes) in glycerol-shocked fibers (whose T tubules vesiculate and are no longer in contact with the external medium); pH recovery in large vesicles made from surface membrane; Na uptake into small vesicles made from either surface or T tubular membrane; and acid extrusion into the T tubular lumen, using impermeable pH-sensitive fluorescent dyes. ii) Does acidification of unstirred layers, especially the T tubular lumen, limit the rate and extent of pHi recovery? The effect of unstirred layers will be assessed by measuring recovery in single vs. multicellular preparations and in fibers exposed to varying external buffer concentrations. The effect of acid extrusion on the pH in unstirred layers will be directly determined using pH- sensitive electrodes close to the fiber surface and using pH- sensitive fluorescent dyes in the T tubular lumen. iii) How does the ability to regulate pH differ in red vs. white muscle fibers? The buffering power, the rate and extent of pHi recovery, and the properties of the transport systems responsible for recovery will be compared in mouse soleus (red) and EDL (white) muscles. These studies will represent the first localization of a carrier system in muscle membrane, the first direct measurements of pH in the T tubular lumen and the first correlation of pH-regulating capabilities with cellular metabolic and contractile properties. Beyond the basic understanding of pH regulation gained in these studies, detailed knowledge of pH regulation may shed light on the etiology and/or symptoms of the muscular dystrophies and myotonias. One of the primary lesions of these diseases is an alteration of membrane properties which results in altered contractile and metabolic processes. The role that changes in pHi regulating ability may play in such pathology remains to be studied.