Hirota K, Ito Y, Kuze S, Momose Y
Department of Anesthesiology, Faculty of Medicine, Toyama Medical and Pharmaceutical University.
Masui. 1991 Oct;40(10):1513-9.
In order to analyze direct action of isoflurane on myocardium, we studied effects of isoflurane on membrane potentials and transmembrane ionic currents in single ventricular myocytes isolated enzymatically from rabbit hearts. Membrane potentials were recorded with a suction microelectrode technique, and an action potential was elicited by a brief intracellular stimulus. Isoflurane 3% depressed the action potential overshoot, plateau phase and duration without changing resting potential. Isoflurane decreased the refractory period of the action potential and prolonged the time-constant (tau) of the recovery process. In corresponding voltage clamp experiments, isoflurane significantly depressed the Ca2+ current (ICa), which generates the plateau phase. However, isoflurane had no effect on the transient outward current (I(t)), which triggers repolarization of the action potential. In rabbit ventricular cells, the time- and voltage-dependent outward K+ current (IK) was nearly absent. In conclusion, the depression of the action potential plateau by isoflurane is due to the decrease of ICa. Since isoflurane has no effect on It, the depression of the plateau phase by isoflurane may explain the shortening in the duration and the refractory period of the action potential.
为了分析异氟烷对心肌的直接作用，我们研究了异氟烷对从兔心脏酶解分离的单个心室肌细胞的膜电位和跨膜离子电流的影响。采用吸引微电极技术记录膜电位，通过短暂的细胞内刺激诱发动作电位。3%的异氟烷降低动作电位的超射、平台期和时程，而不改变静息电位。异氟烷缩短动作电位的不应期，延长恢复过程的时间常数（τ）。在相应的电压钳实验中，异氟烷显著抑制产生平台期的Ca2+电流（ICa）。然而，异氟烷对触发动作电位复极化的瞬时外向电流（I(t)）没有影响。在兔心室细胞中，几乎不存在时间和电压依赖性外向K+电流（IK）。总之，异氟烷对动作电位平台期的抑制是由于ICa的降低。由于异氟烷对I(t)没有影响，异氟烷对平台期的抑制可能解释了动作电位时程和不应期的缩短。
