Modulation by cytoskeletons of ATP-sensitive K and voltage-dependent K channels in vascular cells.

采用全细胞电压钳和单通道电流记录方法，研究鬼笔环肽和细胞松弛素B或D对胶原酶分离的兔门静脉ATP敏感性钾通道活性的影响。当细胞松弛素D（20 μ M）加入到移液管中时，吡那地尔（100 μ M）诱导的电流的最大幅度不被细胞松弛素D改变（在细胞松弛素存在下，95* 74 pA;在细胞松弛素不存在下，97*59 ; n=22）。然而，当比较从同一动物获得的吡那地尔诱导电流的最大振幅的平均值时，细胞松弛素处理的细胞中的吡那地尔诱导电流的振幅总是小于未处理的细胞（60*40% ; n=22）。在6个细胞中的3个中，当细胞松弛素D（20 μ M）同时应用于灌流液中时，细胞松弛素D降低了吡那地尔诱导的电流的幅度。然而，在其余细胞中应用细胞松弛素D没有观察到变化。另一方面，细胞外应用鬼笔环肽（20 μ M）在12个细胞中的4个中增加了吡那地尔诱导的电流，在12个细胞中的2个中降低了电流。在细胞外应用鬼笔环肽的其他细胞中未观察到变化。鬼笔环肽（10 μ M）不改变细胞贴壁条件下吡那地尔诱导的单通道电流活性。一个'跑下来'的现象，记录的膜切除，没有防止鬼笔环肽。此外，鬼笔环肽并没有改变由内而外的膜条件下诱导的单通道电流的活动与GDP的吡那地尔。细胞松弛素B和细胞松弛素D既不抑制单通道电流的幅度，也不抑制平均开放时间。这些结果表明，与心肌细胞ATP敏感性钾通道相比，门静脉细胞骨架可能不参与ATP敏感性钾通道活性的调节。

Effects of phalloidin and cytochalasin B or D were investigated on the activities of the ATP-sensitive K channels in the rabbit portal vein isolated by collagenase using whole-cell voltage-clamp and single channel current recording methods. When cytochalasin D (20muM) were applied in the pipette, the maximum amplitude of the pinacidil (100muM) -induced current was not changed by cytochalasin D (in the presence of cytochalasin, 95*74pA ; in the absence of cytochalasin, 97*59 ; n=22). However, when mean values of the maximum amplitudes of the pin acidil-induced current obtained from the same animal were compared, the amplitude of the pinacidil-induced current was always smaller in cytochalasin-treated cells than in untreated cells (60*40% ; n=22). In 3 out of 6 cells, cytochalasin D (20muM) reduced the amplitude of the pinacidil-induced current, when cytochalasin was simultaneously applied in the superfusate. However, no change was observed by application of cytochalasin D in the rest of cells. On the other hand, extracellularly application of phalloidin (20muM) increased the pinacidil-induced current in 4 out of 12 cells, reduced the current in 2 out of 12 cells. No change was seen in other cells by extracellularly application of phalloidin. Phalloidin (10muM) did not change the activity of the single channel current induced by pinacidil observed in cell-attached condition. A 'run-down' phenomenon, recorded by the membrane excision, was not prevented by phalloidin. Furthermore, phalloidin did not change the activity of the single channel currents induced by pinacidil with GDP in the inside-out membrane patch condition. Cytochalasin B and cytochalasin D inhibit neither amplitude nor mean open time of the single channel current. These results indicated that cytoskeletons in the rabbit portal vein might not participate the modulation on the channel activity of the ATP-sensitive K channels, in comparison to the ATP-sensitive channels in the cardiac celk.