Nakaya H, Kimura S, Kanno M
Am J Physiol. 1985 Dec;249(6 Pt 2):H1078-85. doi: 10.1152/ajpheart.1985.249.6.H1078.
To gain a better understanding of the ionic mechanisms responsible for the electrophysiological disturbances occurring during myocardial ischemia, transmembrane potentials and intracellular potassium (aiK) and sodium (aiNa) ion activities were measured under individual and combined conditions of hypoxia (Po2 less than 50 mmHg), respiratory acidosis (pH 6.6), and no glucose in isolated epicardial ventricular muscle preparations of the canine heart using conventional and ion-selective microelectrode techniques. After 30 min superfusion with hypoxic, acidic, and glucose-free solution under 2-Hz stimulation, resting membrane potential (RMP) was significantly reduced from -85.5 +/- 0.6 to -69.5 +/- 1.0 mV, accompanied by decreases in action potential amplitude, maximum upstroke velocity of phase O, and action potential duration. aiK was significantly decreased from 101.0 +/- 5.6 to 79.5 +/- 5.8 mM, whereas aiNa was not significantly altered by the combined condition. RMP and aiK were moderately decreased by hypoxia alone, slightly decreased by acidosis, and hardly affected by the glucose-free condition. The extent of depolarization was well correlated with the decrease in aiK. These results suggest that Na+-K+ pump inhibition may not be a major cause of K+ efflux from myocardial cells under the hypoxic, acidic, and glucose-free condition and that hypoxia is the most important factor affecting aiK and RMP among these conditions.
为了更好地理解心肌缺血期间发生电生理紊乱的离子机制，在犬心离体心外膜心室肌制备物中，采用传统微电极技术和离子选择性微电极技术，在低氧（氧分压小于50 mmHg）、呼吸性酸中毒（pH 6.6）和无葡萄糖的单独及联合条件下，测量跨膜电位以及细胞内钾（aiK）和钠（aiNa）离子活性。在2 Hz刺激下用低氧、酸性和无葡萄糖溶液灌注30分钟后，静息膜电位（RMP）从-85.5±0.6 mV显著降低至-69.5±1.0 mV，同时动作电位幅度、0期最大上升速度和动作电位持续时间均降低。aiK从101.0±5.6 mM显著降低至79.5±5.8 mM，而联合条件下aiNa无显著变化。单独低氧使RMP和aiK适度降低，酸中毒使其轻度降低，无葡萄糖条件几乎不影响它们。去极化程度与aiK的降低密切相关。这些结果表明，在低氧、酸性和无葡萄糖条件下，Na+-K+泵抑制可能不是心肌细胞钾外流的主要原因，并且在这些条件中，低氧是影响aiK和RMP的最重要因素。
