PH REGULATION IN SKELETAL MUSCLE--DESIGN & PLASTICITY

脊椎动物骨骼肌调节细胞内pH的能力 (pHi)很少受到关注，尽管事实上， pHi可对肌肉收缩和代谢具有显著影响。 仅在 两块肌肉，青蛙的半腱肌和老鼠的比目鱼肌， 膜转运系统负责pH调节进行了描述。 在拟议的研究中，将解决三个问题，目的是 更全面地定义肌细胞功能和pHi之间的关系 调控 i）青蛙肌肉中的pH调节系统（Na/H和 (Na+ HCO 3）/C1交换器）定位于表面膜，T管 膜或两者？ 运输车的本地化将通过以下方式实现： 研究：甘油冲击纤维的pH恢复（用玻璃电极） （其T小管囊状化，不再与外部细胞接触） 培养基）;由表面膜制成的大囊泡中的pH恢复; Na + 摄取到由表面或T管膜制成的小泡中; 和酸挤压到T管腔，使用不可渗透的pH敏感的 荧光染料。 ii）未搅拌层的酸化，特别是 T管管腔，限制pHi恢复的速率和程度？ 效果 将通过测量单个与未搅拌层的回收率来评估。 多细胞制剂和暴露于不同外部缓冲液的纤维中 浓度的 酸挤压对非搅拌层pH值的影响 将直接使用接近的pH敏感电极测定 纤维表面和使用pH敏感的荧光染料在T管 流明 iii）红色与白色的调节pH的能力有何不同 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性质将 在小鼠比目鱼肌（红色）和EDL（白色）肌肉中进行比较。 这些研究 将代表载体系统在肌肉中的首次定位 膜，第一次直接测量pH值的T管管腔， pH调节能力与细胞代谢的第一个相关性 和收缩性能。 超越对pH值的基本理解 在这些研究中获得的调节，pH调节的详细知识， 阐明肌营养不良症的病因和/或症状， 肌强直 这些疾病的主要病变之一是 导致收缩和代谢的改变 流程. pHi调节能力的变化可能在 这种病理学仍有待研究。

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.