Lee C O, Kang D H, Sokol J H, Lee K S
Biophys J. 1980 Feb;29(2):315-30. doi: 10.1016/S0006-3495(80)85135-6.
The intracellular Na ion activity (aiNa) and the contractile tension (T) of sheep cardiac Purkinje fibers were simultaneously measured employing recessed-tip Na+-selective glass microelectrodes and a mechano-electric transducer. The aiNa of 6.4 +/- 1.6 mM (mean +/- SD, n = 56) was obtained in fibers perfused with normal Tyrode's solution. The changes in aiNa and T were measured during and after the exposure of fibers to a cardiac glycoside, dihydro-ouabain (DHO) in concentrations between 5 X 10(-8) M and 10(-5) M. The exposure time to DHO was 15 min. Both aiNa and T did not change in fibers exposed to 5 X 10(-8) M DHO, and the threshold concentration for the effect of DHO appeared to be around 10(-7) M. In DHO concentrations greater than the threshold, the increases in aiNa and T strongly correlated during the onset of DHO effects. The recoveries of aiNa and T were variable and slow, being dependent on the DHO concentration. In those fibers which recovered from the effects of DHO, the time-course of aiNa recovery was similar to that of T recovery. In fibers exposed to DHO of 5 X 10(-6) M or greater, the apparent toxic effects were observed in both action potential and contraction after an initial increase in T. The fibers manifesting the apparent toxic effects has a aiNa of approximately 30 mM or greater. The results of this study indicate that the increase in aiNa is associated with the positive inotropic action of the cardiac glycoside.
采用凹形尖端钠离子选择性玻璃微电极和机电换能器，同时测量了绵羊心脏浦肯野纤维的细胞内钠离子活性（aiNa）和收缩张力（T）。在用正常台氏液灌注的纤维中，测得aiNa为6.4±1.6 mM（平均值±标准差，n = 56）。在纤维暴露于浓度为5×10⁻⁸ M至10⁻⁵ M的强心苷二氢哇巴因（DHO）期间及之后，测量aiNa和T的变化。DHO的暴露时间为15分钟。暴露于5×10⁻⁸ M DHO的纤维中，aiNa和T均未改变，DHO产生效应的阈值浓度似乎约为10⁻⁷ M。在高于阈值的DHO浓度下，DHO效应开始时，aiNa和T的增加密切相关。aiNa和T的恢复是可变且缓慢的，取决于DHO的浓度。在从DHO效应中恢复的那些纤维中，aiNa恢复的时间进程与T恢复的相似。在暴露于5×10⁻⁶ M或更高浓度DHO的纤维中，在T最初增加后，动作电位和收缩均出现明显的毒性作用。表现出明显毒性作用的纤维，其aiNa约为30 mM或更高。本研究结果表明，aiNa的增加与强心苷的正性肌力作用相关。
