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首页> 美国卫生研究院文献>The Journal of Physiology >Calcium channel inactivation in frog (Rana pipiens and Rana moctezuma) skeletal muscle fibres.
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Calcium channel inactivation in frog (Rana pipiens and Rana moctezuma) skeletal muscle fibres.

机译：青蛙（林蛙和林蛙）骨骼肌纤维中的钙通道失活。

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The decay of the Ca2+ current (ICa) during a maintained depolarization was studied in intact twitch skeletal muscle fibres of Rana pipiens and Rana moctezuma with the three-micro-electrode voltage-clamp technique. ICa was recorded at 23 degrees C, after blocking K+ currents, in TEA methanesulphonate saline with 10 mM-Ca2+ made hypertonic by adding 350 mM-sucrose. In two-pulse experiments, ICa during the test pulse was reduced to about 80% (R. pipiens) or 50% (R. moctezuma) of the control value, without any detectable inward ICa during 7 s conditioning pre-pulses. The experimental points of the steady-state inactivation curve (h infinity) were fitted to h infinity = (1 + exp [Em - Vh)/kh]-1, where Em is the membrane potential and with Vh = -33 +/- 3 mV and kh = 6 +/- 1 mV for R. pipiens, and Vh = -44 +/- 3 mV and kh = 9.5 +/- 1.0 mV for R. moctezuma. The rate constant of decay for inactivated currents (range -8 to -47 mA cm-3) and for control currents (range -23 to -62 mA cm-3), was independent of ICa amplitude. The average rate constant of decay at 0 mV was 1.18 +/- 0.02 s-1 (66). These results indicate that in intact fibres under hypertonic solution ICa decay can be explained by a voltage-dependent inactivation process and not by depletion of tubular Ca2+. The absence of depletion could be due to a large fractional tubular volume or to the presence of a Ca2+ pump in the tubular system.
机译：利用三微电极电压钳技术研究了皮脂树蛙和林蛙的完整抽搐骨骼肌纤维中Ca2 +电流（ICa）在维持的去极化过程中的衰减。阻断K +电流后，在23摄氏度下通过添加350 mM蔗糖在含10 mM-Ca2 +的TEA甲磺酸盐溶液中以高渗的形式记录ICa。在两脉冲实验中，测试脉冲期间的ICa降低至对照值的80％（pipiens）或对照的50％（青蒿），而在7 s的预处理预脉冲期间没有任何可检测到的内向ICa。将稳态灭活曲线的实验点（h无穷大）拟合为h无穷大=（1 + exp [Em-Vh）/ kh] -1，其中Em是膜电位，Vh = -33 +/-对于pipiens，3 mV和kh = 6 +/- 1 mV，对于R. moctezuma，Vh = -44 +/- 3 mV，kh = 9.5 +/- 1.0 mV。灭活电流（-8至-47 mA cm-3的范围）和控制电流（-23至-62 mA cm-3的范围）的衰减速率常数与ICa幅度无关。 0 mV时的平均衰减率常数为1.18 +/- 0.02 s-1（66）。这些结果表明，在高渗溶液中完整纤维中的ICa衰减可以通过电压依赖性失活过程来解释，而不是通过管状Ca2 +的耗尽来解释。耗尽的原因可能是由于大比例的管状体积或管状系统中存在Ca2 +泵。

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