Itoh T, Kajiwara M, Kitamura K, Kuriyama H
J Physiol. 1982 Jan;322:107-25. doi: 10.1113/jphysiol.1982.sp014026.
Effects of acetylcholine (ACh), caffeine and procaine on the membrane and mechanical properties of the intact and skinned muscle cells of the porcine coronary artery were investigated using the micro-electrode and isometric tension recording methods.1. ACh (10(-8)-10(-5)m) had no effect on the membrane potential and membrane resistance, as assessed from the current-voltage relationship.2. Caffeine possessed dual actions on the membrane property, i.e. a low concentration (0.3-1 mm) hyperpolarized and a high concentration (over 1 mm) depolarized the membrane, while caffeine (over 0.3 mm) consistently increased the ionic conductance of the membrane. Procaine (over 1 mm) depolarized the membrane and decreased the ionic conductance of the membrane.3. The spike and contraction evoked by outward current pulses in the presence of 10 mm-TEA were suppressed by treatment with caffeine (5 mm) or procaine (3 mm), but the spike was slightly and the electrically induced contraction was significantly suppressed by ACh (10(-6)m) due to the marked increase in resting tension.4. In Ca-free 2 mm-EGTA containing solution, the K-induced contraction (118 mm) rapidly ceased, but not the contraction evoked by ACh (10(-5)m) or caffeine (5 mm). The ACh-induced contraction rapidly ceased in the presence of 1 mm-procaine; however, over 5 mm-procaine was required to abolish the caffeine-induced contraction.5. The pCa-tension relationship was measured in saponin-treated skinned muscles. The minimum concentration of free Ca required to produce contraction was 2 x 10(-7)m, while maximum contraction was observed at 10(-5)m-free Ca. The maximum amplitude of Ca-induced contraction observed in skinned muscles was larger or the same as that evoked by ACh in the intact muscle. ACh (10(-5)m), caffeine (5 mm) and procaine (5 mm) had no effect on the pCa-tension relationship.6. After Ca has been loaded in skinned muscles, caffeine and replacement of K with choline (116 mm) in the Ca-free EGTA containing solution produced the contraction. However, the application of ACh did not result in a release of the stored Ca, and procaine suppressed the release of Ca activated by caffeine.7. The present results indicate that ACh activates the muscarinic receptor distributed on the plasma membrane, thus releasing the stored Ca. However, this mechanism may not be a prerequisite for direct action of ACh on the Ca releasing site. The possible mechanism of ACh action on the Ca releasing site, mainly sarcoplasmic reticulum, was discussed in relation to actions of caffeine and procaine, particularly with regard to the functional relations between plasma membrane and sarcoplasmic reticulum.
采用微电极和等长张力记录方法，研究了乙酰胆碱（ACh）、咖啡因和普鲁卡因对猪冠状动脉完整和去膜肌细胞的膜特性及力学特性的影响。1. 根据电流-电压关系评估，ACh（10⁻⁸ - 10⁻⁵m）对膜电位和膜电阻无影响。2. 咖啡因对膜特性具有双重作用，即低浓度（0.3 - 1mm）使膜超极化，高浓度（超过1mm）使膜去极化，而咖啡因（超过0.3mm）持续增加膜的离子电导。普鲁卡因（超过1mm）使膜去极化并降低膜的离子电导。3. 在10mm - TEA存在下，外向电流脉冲诱发的锋电位和收缩被咖啡因（5mm）或普鲁卡因（3mm）处理所抑制，但由于静息张力显著增加，ACh（10⁻⁶m）使锋电位略有抑制，电诱发收缩则被显著抑制。4. 在含2mm - EGTA的无钙溶液中，K⁺诱导的收缩（118mm）迅速停止，但ACh（10⁻⁵m）或咖啡因（5mm）诱发的收缩未停止。在1mm - 普鲁卡因存在下，ACh诱导的收缩迅速停止；然而，需要超过5mm - 普鲁卡因才能消除咖啡因诱导的收缩。5. 在皂素处理的去膜肌中测量了pCa - 张力关系。产生收缩所需的游离Ca的最低浓度为2×10⁻⁷m，而在游离Ca为10⁻⁵m时观察到最大收缩。在去膜肌中观察到的Ca诱导收缩的最大幅度大于或等于完整肌肉中ACh诱发的收缩幅度。ACh（10⁻⁵m）、咖啡因（5mm）和普鲁卡因（5mm）对pCa - 张力关系无影响。6. 在去膜肌中加载Ca后，咖啡因以及在含无钙EGTA的溶液中用胆碱（116mm）替代K⁺可产生收缩。然而，应用ACh并未导致储存Ca的释放，且普鲁卡因抑制了咖啡因激活的Ca释放。7. 目前的结果表明，ACh激活分布于质膜上的毒蕈碱受体，从而释放储存的Ca。然而，该机制可能不是ACh直接作用于Ca释放位点的先决条件。结合咖啡因和普鲁卡因的作用，特别是关于质膜和肌浆网之间的功能关系，讨论了ACh作用于Ca释放位点（主要是肌浆网）的可能机制。
