Conrad C H, Mark R G, Bing O H
Am J Physiol. 1983 Mar;244(3):H341-50. doi: 10.1152/ajpheart.1983.244.3.H341.
We studied the effects of brief periods (20-30 min) of hypoxia in the presence of 5 and 50 mM glucose and of glycolytic blockade (10(-4) M iodoacetic acid, IAA) on action potentials, membrane currents, and mechanical activity in rat ventricular papillary muscles using a single sucrose gap voltage-clamp technique. Steady-state outward current (iss) was determined at the end of a 500-ms clamp to the test potential following a 600-ms clamp to a holding potential of -50 mV. In the presence of 5 mM glucose, hypoxia resulted in a decrease in action potential duration (APD) and an increase in iss (on the order of 60% at 0 mV) over the potential range studied. The increase in iss did not appear to be due to an increase in leakage current or to a change in the cable properties of the preparation. Addition of 50 mM glucose prevented the change in both APD and iss with hypoxia. In addition, glycolytic blockade with IAA did not alter iss in the presence of oxygen. We conclude that an increase in iss appears to be a major factor in the abbreviation of rat ventricular action potential seen with hypoxia. Glycolysis appears to be a sufficient (with 50 mM glucose) but not necessary source of energy for the maintenance of normal iss.
我们使用单蔗糖间隙电压钳技术，研究了在5 mM和50 mM葡萄糖存在的情况下，短暂缺氧（20 - 30分钟）以及糖酵解阻断（10⁻⁴ M碘乙酸，IAA）对大鼠心室乳头肌动作电位、膜电流和机械活性的影响。在将钳制电位维持在 -50 mV 600 ms后，再将钳制电位施加到测试电位500 ms，然后在该测试电位结束时测定稳态外向电流（iss）。在5 mM葡萄糖存在的情况下，在所研究的电位范围内，缺氧导致动作电位时程（APD）缩短，iss增加（在0 mV时约增加60%）。iss的增加似乎不是由于漏电流增加或标本电缆特性的改变。添加50 mM葡萄糖可防止缺氧引起的APD和iss的变化。此外，在有氧情况下，用IAA阻断糖酵解不会改变iss。我们得出结论，iss增加似乎是缺氧时大鼠心室动作电位缩短的主要因素。糖酵解似乎是维持正常iss的充足（在50 mM葡萄糖存在时）但非必需的能量来源。
