Department of Surgery, Chinese University of Hong Kong, Hong Kong SAR, China.
J Heart Lung Transplant. 2009 Oct;28(10):1094-101. doi: 10.1016/j.healun.2009.06.011.
Large-conductance calcium-activated potassium channels (BK(Ca)) of vascular smooth muscle cells (VSMCs) play an important role in the regulation of vascular tone. We tested the hypotheses that the alteration of arterial relaxation after exposure to ischemia or hyperkalemia is attributable to the alteration in the activities of BK(Ca) by using the patch-clamp technique and force measurement.
VSMCs were enzymatically isolated from porcine coronary arteries, with the primary cultures used for patch-clamp study. BK(Ca) currents were recorded in a whole-cell configuration (n = 5 in each group). The BK(Ca) activator NS1619 (-7 to -4.5 logM)-induced relaxation was studied myographically in small porcine coronary arteries (n = 6 per group). The effects of global ischemia for 1 hour and hyperkalemia (20 to 120 mmol/liter) were tested.
Ischemia for 1 hour markedly reduced the BK(Ca) current from 119.8 +/- 11.4 pA/pF to 86.0 +/- 3.7 pA/pF (p < 0.05). The rise of extracellular K(+) resulted in increased BK(Ca) currents in a concentration-dependent manner (5.4 mmol/liter: 31.6 +/- 3.4 pA/pF; 20 mmol/liter: 73.6 +/- 11.4 pA/pF; 60 mmol/liter: 108.6 +/- 20.6 pA/pF; 120 mmol/liter: 135.2 +/- 20.5 pA/pF; p < 0.05). NS1619-induced relaxation was suppressed by ischemia (71.4 +/- 2.2% vs 95.3 +/- 1.6%; p < 0.01) and was inferior in K(+) pre-contraction, as compared with U(46619) (a thromboxane A(2) mimetic) pre-contraction (p < 0.05).
In coronary circulation: (1) the BK(Ca) current density and related vasorelaxation are reduced after ischemia; and (2) hyperkalemia induces dual effects; the depolarization obscures the compensatory increase of the BK(Ca) activity. These findings imply that BK(Ca) activators may be used in cardioplegia or heart preservation solutions to protect the function of this ion channel.
血管平滑肌细胞（VSMCs）中的大电导钙激活钾通道（BK（Ca））在调节血管张力方面发挥着重要作用。我们通过使用膜片钳技术和力测量来测试以下假设：在暴露于缺血或高钾血症后，动脉弛豫的改变归因于 BK（Ca）活性的改变。
通过酶消化法从猪冠状动脉中分离出 VSMCs，原代培养用于膜片钳研究。在全细胞模式下记录 BK（Ca）电流（每组 5 个）。使用小猪冠状动脉肌电图研究 BK（Ca）激活剂 NS1619（-7 至-4.5 logM）诱导的弛豫（每组 6 个）。测试了 1 小时的整体缺血和高钾血症（20 至 120 mmol/L）的影响。
缺血 1 小时后，BK（Ca）电流从 119.8 +/- 11.4 pA/pF 显著减少至 86.0 +/- 3.7 pA/pF（p < 0.05）。细胞外 K（+）的升高以浓度依赖性方式增加 BK（Ca）电流（5.4 mmol/L：31.6 +/- 3.4 pA/pF；20 mmol/L：73.6 +/- 11.4 pA/pF；60 mmol/L：108.6 +/- 20.6 pA/pF；120 mmol/L：135.2 +/- 20.5 pA/pF；p < 0.05）。NS1619 诱导的弛豫受缺血抑制（71.4 +/- 2.2% vs 95.3 +/- 1.6%；p < 0.01），并且在 K（+）预收缩中比 U（46619）（血栓素 A（2）模拟物）预收缩中较差（p < 0.05）。
在冠状循环中：（1）缺血后 BK（Ca）电流密度和相关的血管舒张减少；（2）高钾血症引起双重作用；去极化掩盖了 BK（Ca）活性的代偿性增加。这些发现表明，BK（Ca）激活剂可用于心脏停搏液或心脏保存液中，以保护该离子通道的功能。
