Contractile activation in scorpion striated muscle fibers. Dependence on voltage and external calcium.
Contractile activation in scorpion striated muscle fibers. Dependence on voltage and external calcium.
复制标题
蝎子横纹肌纤维中的收缩激活。依赖电压和外部钙。
DOI：
10.1085/jgp.84.3.321
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发表时间：
1984-09
影响因子：
3.8
通讯作者：
Scheuer, T
中科院分区：
文献类型：
--
作者：
Gilly, W F;Scheuer, T
利用脊椎动物骨骼肌研究中采用的标准微电极技术，对蝎横纹肌纤维的兴奋-收缩偶联进行了表征。蝎肌的动作电位由再生活动的两个阶段组成。一个相对快速的、过冲的初始尖峰之后是一个较长的、重复的小尖峰的后放电。这种后放电伴随着在复极化时迅速放松的抽搐。在不含钠、含河豚毒素（TTX）或不含钙的培养基中，抽搐失败。然而，咖啡因会导致肌肉痉挛，肌肉被无钠和无钙溶液麻痹。在无钠或含TTX的介质中，用双微电极电压钳制肌纤维一点的实验表明：（a）阈收缩的强度-时程关系具有与蛙肌相似的形状，但平均值向正方向偏移约20 mV，（B）丁卡因对蝎肌和蛙肌的强度-时程曲线有平行效应，而对蛙肌的强度-时程曲线有平行效应。（c）蝎的收缩激活在无钙介质中被消除;和（d）收缩阈值与所有持续时间的脉冲的内向钙电流的发生高度相关。因此，蝎子和青蛙肌肉收缩激活的电压依赖性是相似的。然而，不同的制剂依赖于细胞外钙收缩。这些结果进行了讨论有关的可能机制耦合管去极化钙释放肌浆网在脊椎动物和无脊椎动物骨骼肌。
Excitation-contraction coupling was characterized in scorpion striated muscle fibers using standard microelectrode techniques as employed in studies on vertebrate skeletal muscle. The action potential of scorpion muscle consists of two phases of regenerative activity. A relatively fast, overshooting initial spike is followed by a prolonged after- discharge of smaller, repetitive spikes. This after-discharge is accompanied by a twitch that relaxes promptly upon repolarization. Twitches fail in Na-free, tetrodotoxin (TTX)-containing, or Ca-free media. However, caffeine causes contractures in muscles paralyzed by Na- and Ca-free solutions. Experiments on muscle fibers voltage-clamped at a point with two microelectrodes in Na-free or TTX-containing media indicate that: (a) the strength-duration relation for threshold contractions has a shape similar to that in frog muscle, but mean values are displaced approximately 20 mV in the positive direction; (b) tetracaine exerts a parallel effect on strength-duration curves from scorpion and frog; (c) contractile activation in scorpion is abolished in Ca-free media; and (d) the contractile threshold is highly correlated with the occurrence of inward Ca current for pulses of all durations. Thus, the voltage dependence of contractile activation in scorpion and frog muscle is similar. However, the preparations differ in their dependence on extracellular Ca for contraction. These results are discussed in relation to possible mechanisms coupling tubular depolarization to Ca release from the sarcoplasmic reticulum in vertebrate and invertebrate skeletal muscle.