缺氧对平滑肌膜电位的影响

新鲜分离的猪肺叶内动脉，予以１００％氧气平衡，记录并连续观察其平滑肌膜电位。实验发现，通１００％氮气以降低氧张力时，可引起膜电位快速的超极化反应及其后持续的去极化。去除内皮或细胞外钙离子可致超极化反应完全消失，并使去极化程度降低。提示缺氧引起的超极化反应依赖于内皮和细胞外钙。由此推测缺氧通过外钙内流刺激肺动脉内皮细胞释放内皮源性超极化因子，参与调节急性缺氧性肺血管收缩反应。本实验还记录到平滑肌细胞静息膜电位自发性振荡，缺氧可使其振幅降低，振荡频率稍慢

Effects of Hypoxia on Membrane Potential of Pulmonary Artery

In fresh isolated segments of the intrapulmonary artery of the porcine, the membrane potential of smooth muscle cell was recorded and observed continuously.Lowing of oxygen tension(prebubbling with 100% O_2) by 100% N_2 led to a rapid hyperpolarization,which followed by a sustained depolarization. The hyperpolarization response was abolished completely by removal of endothelium and extracellular Ca~(2+),under which a reduced depolarization response still remained.The experiment indicated that the hypoxia induced hyperpolarization was both endothelium and extracellular Ca~(2+) dependent.It was referred that the hypoxia induced Ca~(2+) influx could stimulate the release of endothelium derivedhyperpolarization factor contributing to the modulation of hypoxic pulmonary vasoconstriction.The experiment has recorded the spontaneous oscillations of resting membrane potential, and found that hypoxia clearly decreased the amplitude of the oscillations and slightly reduced its frequency.