Macroscopic K+ currents in single smooth muscle cells of the rabbit portal vein.
Macroscopic K+ currents in single smooth muscle cells of the rabbit portal vein.
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兔门静脉单个平滑肌细胞中的宏观 K 电流。
DOI：
10.1113/jphysiol.1989.sp017641
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Leblanc,N
中科院分区：
文献类型：
--
作者：
Hume,JR;Leblanc,N
1. 从兔门静脉分离的单个平滑肌细胞在室温下使用膜片钳技术的全细胞结构进行电压夹紧。这些细胞的平均静息电位为‐47.9 mV，平均输入电阻为376 M ω。2. 使用小针尖直径的微移液器（为了避免细胞透析），从- 50 mV保持电位出发的去极化电压箝位脉冲引发了两个不同的向外电流：准瞬时背景电流和时间相关电流，但似乎没有灭活（延迟整流器）。当返回保持电位时，观察到向外的尾电流衰减回保持电流。3. 尾电流发展的时间过程，根据尾电流协议的包络估计，遵循在前一个测试脉冲期间引发的延迟整流器的激活动力学。尾电流反向接近K+离子的平衡电位，表明它主要由钾离子携带。4. 使用大针尖直径的微移液器内部透析细胞（EGTA = 0.1 mM; ATP = 5 mM），发现了两个具有瞬态动力学的额外外向电流：平滑瞬态外向电流（Ito）和自发瞬态外向电流（STOCs）。Ito主要对K+离子具有选择性，并表现出电压依赖性失活，在- 40 mV附近具有一半最大可用性。从洗浴液中去除钙可以显著降低背景电流，消除Ito和STOCs。延迟的整流器电流似乎对这个过程不敏感。当EGTA在微管内升高到5mm时，没有记录到这两种瞬时向外电流，而背景电流和延迟整流电流则不受影响。这些结果表明，Ito和自发瞬态向外电流是由内部钙激活的。6. 外用TEA（0.5‐20 mM）阻断所有四个向外电流。钡替代钙显著降低了背景电流和Ito，对延迟整流电流影响较小。当移液管内的钾被铯（130毫米）和TEA（20毫米）取代时，没有观察到上述的向外电流。在用该溶液透析的约60%的细胞中，发现了一个小的内向Ca2+电流。7. 在对照条件下，外用咖啡因（5mm）可消除细胞中的STOCs。在控制条件下缺乏这种活动的细胞中，咖啡因诱导并随后消除了这种电流。（摘要删节为400字）
1. Single smooth muscle cells isolated from rabbit portal vein were voltage clamped at room temperature using the whole‐cell configuration of the patch‐clamp technique. These cells exhibited a mean resting potential of ‐47.9 mV and a mean input resistance of 376 M omega. 2. Using small tip diameter micropipettes (to avoid dialysis of the cells), depolarizing voltage‐clamp pulses from a holding potential of ‐50 mV elicited two distinct outward currents: a quasi‐instantaneous background current and a time‐dependent current that did not appear to inactivate (delayed rectifier). Upon return to the holding potential, an outward tail current decaying back to the holding current was observed. 3. The time course of development of the tail current as estimated from envelopes of tail current protocols followed the kinetics of activation of the delayed rectifier elicited during the preceding test pulse. The tail current reversed close to the equilibrium potential for K+ ions indicating that it is mainly carried by potassium ions. 4. Using large tip diameter micropipettes to internally dialyse the cells (EGTA = 0.1 mM; ATP = 5 mM), two additional outward currents having transient kinetics were revealed: a smooth transient outward current (Ito) and spontaneous transient outward currents (STOCs). Ito was found to be mainly selective for K+ ions and exhibited voltage‐dependent inactivation with half‐maximal availability near ‐40 mV. 5. Removal of calcium from the bathing solution significantly reduced the background current and abolished both Ito and STOCs. The delayed rectifier current appeared to be insensitive to this procedure. The two types of transient outward currents were never recorded when EGTA was elevated to 5 mM inside the micropipette whereas the background and delayed rectifier currents were not affected. These results suggested that Ito and the spontaneous transient outward currents are activated by internal calcium. 6. External application of TEA (0.5‐20 mM) blocked all four outward currents. Calcium replacement by barium significantly reduced the background current and Ito, and had small effects on the delayed rectifier current. When potassium was replaced with caesium (130 mM) and TEA (20 mM) inside the pipette, none of the outward currents described was ever observed. In about 60% of the cells dialysed with this solution a small inward Ca2+ current was revealed. 7. External application of caffeine (5 mM) abolished STOCs in cells in which this activity was present under control conditions. In cells lacking this type of activity under control conditions caffeine induced and later abolished this type of current.(ABSTRACT TRUNCATED AT 400 WORDS)