大鼠肠系膜细动脉血管平滑肌大电导钙激活钾通道的特性

Properties of large-conductance calcium-activated potassium channel in rat mesenteric arteriole smooth muscle cells

目的探讨肠系膜细动脉血管平滑肌细胞膜上大电导钙激活钾通道(large-conductance calcium-activated potassium channel, BKCa)的电生理特性及其与张力调节的可能机制。方法木瓜酶、胶原酶两步消化法急性分离大鼠肠系膜细动脉血管平滑肌细胞,膜片钳的内面向外式记录法记录BKCa。结果(1)在浴槽液和电极液均为高钾的条件下,BKCa通道的单通道电导为(221±6)pS,反转电位为-0.12 mV;(2)BKCa通道的电流幅度无细胞内钙依赖性,而开放概率(NPo)则同时具有电压依赖性和细胞内钙依赖性。在细胞内钙浓度为0.1 μmol/L时, 使NPo增加e倍的电压增加为(13±1)mV, 达到最大开放概率一半的电压(V1/2)为(22±2)mV;(3)在细胞内钙浓度为1 μmol/L时,可记录到通道长时间的关闭和失活现象,这种现象称为钙依赖性失活。结论肠系膜细动脉血管平滑肌细胞膜上的BKCa具有大电导、高钾选择性、强电压依赖性和高度的细胞内钙敏感性。BKCa高度的钙敏感性可能与血管平滑肌病理情况下的代偿调节有关。

Objective To investigate the electrophysiological properties of large-conductance calcium-activated potassium channel (BK Ca ) in mesenteric arteriole smooth muscle cells of rat. Method Mesenteric arteriolar smooth muscle cells from rats were isolated and inside-out patch clamp technique was used to study BK Ca . Results The single channel conductance of BK Ca recorded was 221±6 pS and the reversal potential was -0.12 mV in the presence of high potassium in the bathing and pipette solutions. The open probability (NPo) of the channel was both voltage- and intracellular calcium- dependent, whereas the amplitude of the channel was not calcium-dependent. Prolonged closed state could be observed at intracellular calcium concentrations of 1 μmol/L or above, known as calcium-dependent inactivation. Conclusion BK Ca in rat mesenteric arterial smooth muscle cells has the properties of large conductance, high potassium selectivity, steep voltage dependence and high calcium sensitivity. The high sensitivity to calcium of BK Ca may be related to the compensatory regulation of the smooth muscles in pathophysiological conditions.