Sigurdsson S B, Grampp W
Pflugers Arch. 1981 Jul;391(1):44-8. doi: 10.1007/BF00580693.
The effect of hypoxia on the electrical and mechanical activity of rat portal vein smooth muscle were investigated using intracellular microelectrode technique in combination with contraction force measurements. In control conditions the "resting" potential of the muscle cells was -58.0 +/- 0.1 mV (mean +/- S.E.). Bursts of action potentials, 5-10s long, appeared at regular intervals (2-3/min) in association with phasic contractions. In hypoxia (PO2 at about 10 mm Hg) there was a marked decrease in force and, often, a moderate increase in rate of the spontaneous contractions. Electrically, these changes corresponded to a decrease in length and an increase in frequency of the bursts of action potentials. The general level of membrane polarization and individual action potentials were not affected. In prolonged hypoxia there was a tendency towards dissociation of the electrical and mechanical activities. Increasing [K+]0 or reducing [Na+]0 produced a restoration of the hypoxically depressed force development. Qualitatively similar results with respect to the depression of myogenic activity by hypoxia, and its alleviation in decreased [K+]0 and reduced [Na+]0, were obtained in low Ca (1 mM) solutions. The effects of hypoxia, and their variation with [K+]0 and [Na+]0, could be explained on the basis of pH dependent electro-mechanical uncoupling.
采用细胞内微电极技术结合收缩力测量，研究了缺氧对大鼠门静脉平滑肌电活动和机械活动的影响。在对照条件下，肌肉细胞的“静息”电位为-58.0±0.1 mV（平均值±标准误）。与阶段性收缩相关，每隔2-3分钟有规律地出现5-10秒长的动作电位爆发。在缺氧状态下（PO2约为10 mmHg），收缩力显著下降，且自发收缩频率常适度增加。在电活动方面，这些变化对应于动作电位爆发的长度减小和频率增加。膜极化的总体水平和单个动作电位未受影响。在长时间缺氧时，电活动和机械活动有解离的趋势。增加[K+]0或降低[Na+]0可使缺氧时降低的力产生恢复。在低钙（1 mM）溶液中，关于缺氧对肌源性活动的抑制及其在降低[K+]0和降低[Na+]0时的缓解，获得了定性相似的结果。缺氧的影响及其随[K+]0和[Na+]0的变化，可以基于pH依赖性电-机械解偶联来解释。
