Different effects of raised [K+](0) on membrane potential and contraction in mouse fast- and slow-twitch muscle
Different effects of raised [K+](0) on membrane potential and contraction in mouse fast- and slow-twitch muscle
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DOI：
10.1152/ajpcell.1997.273.2.c598
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发表时间：
1997-08-01
影响因子：
5.5
通讯作者：
Loiselle, DS
中科院分区：
文献类型：
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作者：
Cairns, SP;Hing, WA;Loiselle, DS
将细胞外K+浓度（[K+]（o））从4 mM增加到7-14 mM降低了小鼠分离的慢收缩比目鱼肌和快收缩趾长伸肌（EDL）肌肉中的强直力和静息膜电位（E-m）。强直力-[K+]（o）关系显示，比目鱼肌中超过8-11 mM [K+]（o）的力损失大于EDL，这主要是因为比目鱼肌中每个[K+]（o）下的E-m负性小2-3 mV。强直力-静息E-m关系显示，力在两个阶段中降低：第1阶段（E-m < -60 mV），力下降20%，其中在比目鱼肌和EDL中叠加了该关系;第2阶段（E-m-60至-55 mV），力明显下降，在EDL中比比目鱼肌更陡。此外，在第2阶段，较长的刺激脉冲恢复强直力;抽搐力-刺激强度关系向更高的电压转移;咖啡因，肌浆Ca 2+浓度电梯，增加最大力;抽搐力突然下降。我们认为：1）K+-抑制力是由于动作电位曲线改变（第1阶段）导致的Ca 2（+）释放减少和动作电位阈值增加（第2阶段）导致的不可兴奋纤维，2）当K+引起去极化至约-60 mV时，K+会导致快肌和慢肌的疲劳。
Increasing extracellular K+ concentration ([K+](o)) from 4 to 7-14 mM reduced both tetanic force and resting membrane potential (E-m) in isolated slow-twitch soleus and fast-twitch extensor digitorum longus (EDL) muscles of the mouse. The tetanic force-[K+](o) relationships showed a greater force loss over 8-11 mM [K+](o) in soleus than EDL, mainly because the E-m was 2-3 mV less negative at each [K+](o) in soleus. The tetanic force-resting E-m relationships show that force was reduced in two phases: phase 1 (E-m < -60 mV), a 20% force decline in which the relationships superimposed in soleus and EDL, and phase 2 (E-m -60 to -55 mV), a marked force decline that was steeper in EDL than soleus. Additionally in phase 2, longer stimulation pulses restored tetanic force; the twitch force-stimulation strength relationship was shifted toward higher voltages; caffeine, a myoplasmic Ca2+ concentration elevator, increased maximum force; and twitch force fell abruptly. We suggest that 1) the K+-depressed force is due to reduced Ca2(+) release resulting from an altered action potential profile (phase 1) and inexcitable fibers due to an increased action potential threshold (phase 2), and 2) K+ contributes to fatigue in both fast- and slow-twitch muscle when it causes depolarization to about -60 mV.