CALCIUM TRANSIENTS IN SINGLE MAMMALIAN SKELETAL-MUSCLE FIBERS
CALCIUM TRANSIENTS IN SINGLE MAMMALIAN SKELETAL-MUSCLE FIBERS
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DOI：
10.1113/jphysiol.1993.sp019617
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发表时间：
1993-04-01
影响因子：
5.5
通讯作者：
STEFANI, E
中科院分区：
文献类型：
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作者：
DELBONO, O;STEFANI, E
1.以Mag-Fura-2(Furaptra)为钙指示剂，在3.6-3.8微米肌节长度和17℃条件下，我们研究了电流电压钳(双凡士林间隙技术)下大鼠趾长伸肌切断纤维肌浆内钙离子浓度的瞬时变化。MAG-Fura-5和Fura-2也被用来表征钙瞬变的某些方面。对单个动作电位的反应峰(Ca~(2+))为4.6+/-0.4微米(n~5)。钙瞬变的峰值时间为4.6+/-0.42ms，半宽为8.2+/-1.5ms，上升相时间常数为1.15+/-0.25ms，衰减期时间常数为3.26+/-0.65ms，动作电位与钙瞬变电位的延迟为2.0+/-0.2ms。在电压钳位条件下，研究了不同电压和脉冲持续时间下的钙离子瞬变过程。上升阶段表现出一个复杂的时间过程，有一个快速的初始上升和第二个分量。这两个组分通过钙离子浓度的平台期或短暂的降低而分开。钙瞬变峰值为10.5+/-1.3微米(n=22)。阻断脉搏后，钙离子浓度呈指数衰减。钙瞬变的衰减时间常数随脉冲电压和脉冲时间的增加而增大，在电压大于+10 mV、脉冲长度大于200ms时达到最大值。对Ca~(2+)瞬变衰减相的分析表明，在纤维重新极化后，只有去除过程起作用。用Melzer，Rios&Schneider模型计算肌浆网钙释放速率。在这些计算中估计的17.2+/-3.1um ms-1(n=10)介于其他作者从切割的青蛙肌肉(10um ms-1)和完整的青蛙纤维(100um ms-1)中获得的值(以安替比林III(AP III)为钙指示剂)。
1. We studied the transient changes in myoplasmic Ca2+ concentration under current- and voltage-clamp (double Vaseline-gap technique) in cut fibres of rat extensor digitorum longus muscle using mag-fura-2 (furaptra) as Ca2+ indicator, at 3.6-3.8 mum sarcomere length and 17-degrees-C. Mag-fura-5 and fura-2 were also used in order to characterize some aspects of the Ca2+ transients.2. The peak (Ca2+] in response to a single action potential was 4.6 +/- 0.4 mum (n 5). The time to peak of the Ca2+ transient was 4.6 +/- 0.42 ms, with half-width of 8.2 +/- 1.5 ms, time constant of the rising phase 1.15 +/- 0.25 ms, time constant of the decaying phase 3.26 +/- 0.65 ms, and delay between action potential and Ca2+ transient 2.0 +/- 0.2 ms.3. Ca2+ transients were studied under voltage-clamp conditions at different voltages and pulse durations. The rising phase showed a complex temporal course with a fast initial increase and a second component. Both components were separated by a plateau or a brief decrease of the Ca2+ concentration. The peak Ca2+ transient was 10.5 +/- 1.3 mum (n = 22).4. After interrupting the pulse, Ca2+ concentration decayed exponentially. The time constant of decay of the Ca2+ transient increased with the pulse voltage and duration, reaching a maximum value at potentials more positive than + 10 mV and pulses longer than 200 ms. An analysis of the decaying phases of the Ca2+ transients suggests that only the removal process operates after fibre repolarization.5. The rate of Ca2+ release from the sarcoplasmic reticulum was calculated using the Melzer, Rios & Schneider model. The value of 17.2 +/- 3.1 mum ms-1 (n = 10) estimated in these calculations was intermediate between those obtained by other authors from cut frog muscles (10 mum ms-1) and intact frog fibres (100 mum ms-1) using antipyrylazo III (AP III) as the Ca2+ indicator.