Sarcoplasmic reticulum calcium release compared in slow-twitch and fast-twitch fibres of mouse muscle
Sarcoplasmic reticulum calcium release compared in slow-twitch and fast-twitch fibres of mouse muscle
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DOI：
10.1113/jphysiol.2003.041608
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发表时间：
2003-08-15
影响因子：
5.5
通讯作者：
Hollingworth, S
中科院分区：
文献类型：
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作者：
Baylor, SM;Hollingworth, S
实验进行了比较的幅度和时间过程中的钙释放肌浆网（SR）在完整的慢缩和快缩小鼠纤维。在小束内的单个纤维被注入furaptra，一种低亲和力，快速响应的Ca2+指示剂。响应于16摄氏度的单个动作电位，肌浆游离[Ca 2 +]变化的峰值振幅和半持续时间（Delta [Ca 2 +]）在纤维类型之间存在显着差异（慢颤：峰值振幅，9.4 +/-1.0 μ m（平均值+/-SEM）;半持续时间，7.7 +/-0.6ms;快速收缩：峰值幅度18.5 +/-0.5 μ m;半持续时间，4.9 +/-0.3ms）。SR Ca2+释放通过Delta [Ca2 +]估计，计算模型计算Ca2+与主要肌浆Ca2+缓冲液（肌钙蛋白、ATP和小清蛋白）的结合;调整缓冲液浓度和反应速率常数以反映纤维类型差异。响应动作电位，释放的Ca 2+总浓度不同纤维类型之间的钙释放速率（Δ [Ca-T]）和钙释放峰值速率（（d/dt）Δ [Ca-T]）相差约3倍（慢收缩：Delta [Ca-T]，127 +/-7 μ M;（d/dt）Delta [Ca-T]，70 +/-6 μ M ms（-1）;快收缩：Delta [Ca-T]，346 +/-6 μ M;（d/dt）Δ [Ca-T]，212 +/-4 μ M ms（-1））。相反，（d/dt）Delta [Ca-T]的半持续时间在两种纤维类型中非常相似（慢收缩，1.8 +/-0.1 ms;快收缩，1.6 +/-0.0 ms）。当用67 Hz的5次电击序列刺激纤维时，对第二次和随后的电击的（d/dt）Δ [Ca-T]的峰值远小于第一次电击的峰值;随后的峰值（表示为第一个峰值的振幅的一部分）在两种纤维类型中相似（慢颤，0.2 - 0.3;快颤，0.1 - 0.3）。结果支持的结论，个别SR钙释放单位功能相似，在慢收缩和快收缩哺乳动物纤维。
Experiments were carried out to compare the amplitude and time course of Ca2+ release from the sarcoplasmic reticulum (SR) in intact slow-twitch and fast-twitch mouse fibres. Individual fibres within small bundles were injected with furaptra, a low-affinity, rapidly responding Ca2+ indicator. In response to a single action potential at 16 degreesC, the peak amplitude and half-duration of the change in myoplasmic free [Ca2+] (Delta[Ca2+]) differed significantly between fibre types (slow-twitch: peak amplitude, 9.4 +/- 1.0 mum (mean +/- S.E.M.); half-duration, 7.7 +/- 0.6 ms; fast-twitch: peak amplitude 18.5 +/- 0.5 mum; half-duration, 4.9 +/- 0.3 ms). SR Ca2+ release was estimated from Delta[Ca2+] with a computational model that calculated Ca2+ binding to the major myoplasmic Ca2+ buffers (troponin, ATP and parvalbumin); buffer concentrations and reaction rate constants were adjusted to reflect fibre-type differences. In response to an action potential, the total concentration of released Ca2+ (Delta [Ca-T]) and the peak rate of Ca2+ release ((d/dt) Delta [Ca-T]) differed about 3-fold between the fibre types (slow-twitch: Delta[Ca-T], 127 +/- 7 muM; (d/dt) Delta [Ca-T], 70 +/- 6muM ms(-1); fast-twitch: Delta[Ca-T], 346 +/- 6 muM; (d/dt) Delta [Ca-T], 212 +/- 4 muM ms(-1)). In contrast, the half-duration of (d/dt) Delta [Ca-T] was very similar in the two fibre types (slow-twitch, 1.8 +/- 0.1 ms; fast-twitch, 1.6 +/- 0.0 ms). When fibres were stimulated with a 5-shock train at 67 Hz, the peaks of (d/dt) Delta [Ca-T] in response to the second and subsequent shocks were much smaller than that due to the first shock; the later peaks, expressed as a fraction of the amplitude of the first peak, were similar in the two fibre types (slow-twitch, 0.2-0.3; fast-twitch, 0.1-0.3). The results support the conclusion that individual SR Ca2+ release units function similarly in slow-twitch and fast-twitch mammalian fibres.