Bkaily G, Jasmin G, Tautu C, Prochek L, Yamamoto T, Sculptoreanu A, Peyrow M, Jacques D
Department of Physiology and Biophysics, Faculty of Medicine, University of Sherbrooke, Quebec, Canada.
Muscle Nerve. 1990 Oct;13(10):939-48. doi: 10.1002/mus.880131009.
Muscle myotube cultures were obtained from normal and Duchenne muscular dystrophy (DMD) biopsies by using an explant technique. The current-voltage (I/V) curve of the whole sodium (Na+) current (INa) in normal myotubes was similar to that obtained from DMD myotubes. However, the inactivation curve of the whole INa was different in normal myotubes when compared to that obtained from DMD myotubes. Addition of 10(-4) M tetrodotoxin (TTX, a fast INa blocker) decreased the whole INa in both preparations. The inorganic calcium (Ca2+) blocker manganese (Mn2+) completely blocked the remaining TTX-resistant INa of normal myotubes and decreased this current in DMD myotubes leaving behind a TTX- and Mn2(+)-insensitive INa that was insensitive to the Ca2+ blocker desmetoxyverapamil ((-)D888). The slow inward barium current (IBa) of both normal and DMD myotubes was blocked by Mn2+ and (-)D888. However the kinetics of the slow channel in normal myotubes was different from that of DMD myotubes. This study demonstrates the presence of a TTX- and Mn2(+)-insensitive INa in DMD myotubes. This channel may contribute to the increase of intracellular Na+ [( Na]i) in DMD and allow Ca2+ to enter the cells through the Na(+)-Ca2+ exchanger, thus contributing to calcium loading.
通过外植技术从正常和杜氏肌营养不良症（DMD）活检组织中获取肌肉肌管培养物。正常肌管中全钠（Na⁺）电流（INa）的电流 - 电压（I/V）曲线与DMD肌管中获得的曲线相似。然而，与DMD肌管相比，正常肌管中全INa的失活曲线有所不同。添加10⁻⁴ M河豚毒素（TTX，一种快速INa阻滞剂）可降低两种制剂中的全INa。无机钙（Ca²⁺）阻滞剂锰（Mn²⁺）完全阻断了正常肌管中剩余的TTX抗性INa，并降低了DMD肌管中的这种电流，留下对TTX和Mn²⁺不敏感的INa，且对Ca²⁺阻滞剂去甲氧基维拉帕米（（-）D888）不敏感。正常和DMD肌管的缓慢内向钡电流（IBa）均被Mn²⁺和（-）D888阻断。然而，正常肌管中慢通道的动力学与DMD肌管不同。本研究证明DMD肌管中存在对TTX和Mn²⁺不敏感的INa。该通道可能导致DMD细胞内Na⁺浓度（[Na⁺]i）升高，并允许Ca²⁺通过Na⁺-Ca²⁺交换器进入细胞，从而导致钙超载。
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