PH REGULATION IN SKELETAL MUSCLE--DESIGN & PLASTICITY

脊椎动物骨骼肌调节细胞内pH的能力 (Phi)几乎没有受到关注，尽管事实是 PHI对肌肉收缩和新陈代谢有显著影响。仅限于在 青蛙的半腱肌和老鼠的比目鱼肌这两块肌肉都有 描述了负责调节pH的膜转运系统。 在拟议的研究中，将讨论三个问题，目的是 更全面地界定肌肉细胞功能与PHI之间的关系 监管。I)是青蛙肌肉中的pH调节系统(Na/H和 (Na+HCO3)/C1交换器)定位于表面膜，即T管 膜还是两种都要？运输机的本地化将通过以下方式实现 研究：甘油电击纤维的PH值恢复(用玻璃电极) (其T小管泡化，不再与外部接触 介质)；表面膜形成的大小泡的pH恢复；钠 摄取表面膜或T管膜形成的小泡； 和酸挤出到T管腔中，使用不透水的pH敏感 荧光染料。二)对未搅动的地层进行酸化，特别是 T管腔是否限制了PHI恢复的速度和程度？其效果 未搅拌层的数量将通过测量单次与 暴露在不同外部缓冲液中的多细胞制剂和纤维 浓度。挤压酸化对未搅拌蛋鸡pH的影响 将使用接近pH敏感电极直接测定 纤维表面和在T管中使用pH敏感的荧光染料 流明。Iii)红色和白色的人调节pH值的能力有什么不同 肌肉纤维？缓冲能力、PHI恢复的速率和程度， 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 将代表肌肉载体系统的第一个局部化 膜，首次直接测量T管腔内的pH和 PH调节能力与细胞代谢的首次相关性 和收缩特性。超越对PH值的基本理解 在这些研究中获得的调节，关于pH调节的详细知识可以 阐明肌肉营养不良的病因和/或症状 肌强直。这些疾病的主要损害之一是改变。 导致收缩和新陈代谢改变的膜特性 流程。Phi调节能力的改变可能在 这种病理机制还有待研究。

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.