Depletion of Ca2+ in the sarcoplasmic reticulum stimulates Ca2+ entry into mouse skeletal muscle fibres
Depletion of Ca2+ in the sarcoplasmic reticulum stimulates Ca2+ entry into mouse skeletal muscle fibres
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DOI：
10.1111/j.1469-7793.2001.0185b.x
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发表时间：
2001-05-15
影响因子：
5.5
通讯作者：
Ogawa, Y
中科院分区：
文献类型：
--
作者：
Kurebayashi, N;Ogawa, Y
1.分离成年小鼠趾长伸肌(EDL)的肌纤维束，同时测定等长张力和Fura-2信号，以探讨骨骼肌中是否存在电容性钙内流途径。用高K+溶液重复处理肌肉纤维中的肌浆网(SR)，最初没有高K+溶液，然后在肌浆/内质网钙-ATPase(SERCA)抑制剂存在的情况下，成功地耗尽了肌肉纤维中的钙离子。耗尽钙离子的SR使我们第一次令人信服地表明，在小鼠EDL肌肉的完整纤维中，绝大多数电压敏感的钙存储与咖啡因敏感的钙存储重叠。这一结论是基于观察到高K+溶液和咖啡因都不会导致枯竭的肌肉纤维发生痉挛。骨骼肌纤维中存在足够活跃的钙离子内流途径，可以在几分钟内重新填充耗尽的肌浆网。钙离子内流对Ni2+敏感，但对硝苯地平耐药，并受质膜去极化的抑制。通过对Mn2+进入的测量，提供了储存操作的钙进入的证据。只有当肌质网钙离子严重耗竭时，才能观察到Mn2+进入的显著加速。被Ni2+阻断但不被硝苯地平阻断的Mn2+内流与钙内流一样，是向内整流的。这些结果表明，钙离子通道电流类似于其他制剂中所描述的钙离子释放激活的钙通道电流。
1.To examine whether a capacitative Ca2+ entry pathway is present in skeletal muscle, thin muscle fibre bundles were isolated fr om extensor digitorum longus (EDL) muscle of adult mice, and isometric tension and fura-2 signals were simultaneously measured.2. The sarcoplasmic reticulum (SR) in the muscle fibres was successfully depleted of Ca2+ by repetitive treatments with high-K+ solutions, initially in the absence and then in the presence of a sarcoplasmic/endoplasmic reticulum Ca2+-ATPase (SERCA) inhibitor.3. Depletion of the SR of Ca2+ enabled us for the first time to show convincingly that the vast majority of the voltage-sensitive Ca2+ store overlaps the caffeine-sensitive Ca2+ store in intact fibres from mouse EDL muscle. This conclusion was based on the observation that both high-K+ solution and caffeine failed to cause a contracture in the depleted muscle fibres.4. The existence of a Ca2+ influx pathway active enough to refill the depleted SR within several minutes was shown in skeletal muscle fibres. Ca2+ entry was sensitive to Ni2+, but resistant to nifedipine and was suppressed by plasma membrane depolarisation.5. Evidence for store-operated Ca2+ entry was provided by measurements of Mn2+ entry. Significant acceleration of Mn2+ entry was observed only when the SR was severely depleted of Ca2+. The Mn2+ influx, which was blocked by Ni2+ but not by nifedipine, was inwardly rectifying as is the case with the Ca2+ entry. These results indicate that the store-operated Ca2+ entry is similar to the Ca2+ release-activated Ca2+ channel (CRAC) current described in other preparations.