Hogg R C, Wang Q, Helliwell R M, Large W A
Department of Pharmacology and Clinical Pharmacology, St. George's Hospital Medical School, London, UK.
Pflugers Arch. 1993 Nov;425(3-4):233-40. doi: 10.1007/BF00374172.
Spontaneous inward and outward currents were studied with perforated patch recording in freshly dispersed rabbit pulmonary artery smooth muscle cells. With physiological potassium concentrations, spontaneous outward and inward currents were recorded at negative membrane potentials. Ion substitution experiments revealed that the outward and inward currents were respectively potassium and chloride conductance increases. Both conductances were abolished by bath application of caffeine (2-10 mM), which releases calcium from internal stores. The rise time and half-decay time of spontaneous potassium currents were both about 25 ms. The spontaneous chloride current has a rise time of 30 ms and decayed exponentially with a time constant (tau) of 70 ms at -50 mV. The tau value was increased by depolarization and increased e-fold for a change of 99 mV in membrane potential. In every cell examined when the spontaneous currents occurred as biphasic events, typically between -20 mV and -40 mV, outward currents preceded inward currents in over 90% of these events whereas the inward current always preceded the outward current in caffeine- and noradrenaline-evoked responses. An explanation for these data is that there may be localization of some chloride channels with respect to the caffeine-sensitive calcium store.
采用穿孔膜片钳记录技术，对新鲜分离的兔肺动脉平滑肌细胞的自发性内向和外向电流进行了研究。在生理钾浓度条件下，于负膜电位记录到自发性外向和内向电流。离子置换实验表明，外向电流和内向电流分别是钾电导和氯电导的增加。通过向浴槽中加入咖啡因（2 - 10 mM）来释放细胞内储存的钙，可使这两种电导均被消除。自发性钾电流的上升时间和半衰减时间均约为25毫秒。自发性氯电流在 - 50 mV时上升时间为30毫秒，且以70毫秒的时间常数呈指数衰减。该时间常数会因去极化而增加，膜电位变化99 mV时增加至原来的e倍。在每个被检测的细胞中，当自发性电流表现为双相事件时，通常发生在 - 20 mV至 - 40 mV之间，在超过90%的此类事件中，外向电流先于内向电流出现，而在咖啡因和去甲肾上腺素诱发的反应中，内向电流总是先于外向电流。对这些数据的一种解释是，相对于对咖啡因敏感的钙储存库，可能存在一些氯通道的定位。
