Li C, Zeng Y M, Zhuang C X, Liu T F
Department of Physiology, Shantou University Medical College, PRC.
Sci China B. 1993 Jul;36(7):835-44.
The traditional critical membrane potential (CMP), -55(-)-60 mV, which corresponds to effective refractory period (ERP), was anew investigated in guinea pig ventricular muscle fibres. The electrical and contractile responses to the stimulus during repolarization of action potential (AP), particularly from +10 to -60 mV, were observed. One third of 35 tested cells displayed testing action potential (TAP) and local response at > or = -54 mV when they were stimulated by testing pulses in 37 degrees C normal Tyrode's solution. Potential level of TAP which occurred earliest was at -30 mV and that of local response which appeared earliest was at 0 mV during repolarization among 95 systematic tests. Most of the TAPs belonged to the slow response potential type. The ratio of TAP evoked at > or = -54 mV initial membrane potential (IMP) was as high as 86% when the experiment was carried out in 37 degrees C 1.5 mmol KC1/L Tyrode's solution. In view of distribution of IMPs of TAPs, the CMP of ERP in guinea pig ventricular muscle fibres was more positive than traditional CMP measured by Hoffman et al. in dog, sheep Purkinje fibres and had a quite changeable range. The CMP of every cell in ventricular muscle was not all the same, and their CMPs approximated to normal distribution. There was no sharp line separating ERP from relative refractory period in myocardium. Higher temperature and low [K]0 were the important factors elevating CMP of ERP.
在豚鼠心室肌纤维中重新研究了传统的临界膜电位（CMP），即-55（-）-60 mV，它对应于有效不应期（ERP）。观察了动作电位（AP）复极化期间对刺激的电反应和收缩反应，特别是在+10至-60 mV范围内。在37℃的正常台氏液中用测试脉冲刺激时，35个受试细胞中有三分之一在≥-54 mV时表现出测试动作电位（TAP）和局部反应。在95次系统测试中，复极化期间最早出现的TAP电位水平为-30 mV，最早出现的局部反应电位水平为0 mV。大多数TAP属于慢反应电位类型。当实验在37℃的1.5 mmol KCl/L台氏液中进行时，在初始膜电位（IMP）≥-54 mV时诱发TAP的比率高达86%。鉴于TAP的IMP分布情况，豚鼠心室肌纤维中ERP的CMP比Hoffman等人在狗、绵羊浦肯野纤维中测得的传统CMP更正，且范围变化较大。心室肌中每个细胞的CMP并非都相同，它们的CMP近似于正态分布。心肌中ERP与相对不应期之间没有明显的界限。较高的温度和低的[K]0是提高ERP的CMP的重要因素。
