蛋白激酶A在慢性心房颤动患者2型小电导钙激活钾通道调控中的作用

 目的：探讨心房颤动（AF）时心房肌细胞2型小电导钙激活钾通道（SK2通道）功能的改变及蛋白激酶A（PKA）相关途径对SK2通道电流的调节。方法：从体外循环手术中获取右心耳组织，应用改良的急性酶分离法获得人心房单个心肌细胞，采用膜片钳全细胞记录模式进行SK2通道电流记录。对比窦性心律（SR）组和AF组SK2通道电流密度及其在混合电流中所占比例的变化。观察PKA特异性抑制剂H-89对SK2通道电流的作用。采用BCA法和ELISA法检测心房组织总蛋白和PKA的含量。结果：（1）SR组和AF组的SK2通道电流均呈现内向整流特性。AF组SK2通道电流密度明显增高，且在混合电流中所占比例增加。在-130 mV钳制电压下，SR组和AF组SK2通道电流密度分别为(-2.61±0.14) pA/pF和(-6.21±0.59) pA/pF，在混合电流中所占比例分别为(20.01±1.44)%和(42.87±1.79)%，差异均有统计学意义（P<0.05）。（2）H-89能够降低SR组和AF组SK2通道电流密度，且对AF组SK2通道电流密度的抑制更明显。在-130 mV钳制电压下，H-89对SR组和AF组SK2通道电流密度的抑制率分别为(39.27±4.08)%和(76.32±2.94)%；SK2通道电流在混合电流中比例亦下降，抑制率分别为(37.48±4.77)%和(56.40±3.66)%，差异均有统计学意义（P<0.05）。（3）AF使PKA含量下降。SR组和AF组PKA含量分别为(511.91±7.22) ng/L和(444.09±7.88) ng/L，差异有统计学意义（P<0.05）。结论：AF患者心房肌细胞SK2通道电流密度及其在混合电流中比例升高，是AF发生和维持的基础之一，电流改变参与了心房电重构过程。PKA能够通过一定途径调节SK2通道功能，且对AF心房肌细胞SK2通道的调节更为显著。

Protein kinase A regulates small-conductance calcium-activated potassium type 2 channel in chronic atrial fibrillation patients

AIM：To investigate the alteration of small-conductance calcium-activated potassium type 2 (SK2) channel currents in atrial myocytes from atrial fibrillation (AF) patients, and the relationship between protein kinase A (PKA) and SK2 channel. METHODS：Right auricular tissues were obtained from the patients undergoing open-heart surgery with extracorporeal circulation. Single atrial myocytes were isolated by modified enzymatic dissociation method. The SK2 channel currents in the isolated human atrial myocytes were recorded using whole-cell patch-clamp technique. The alteration of SK2 channel currents and the regulation of SK2 channel by PKA were compared between sinus rhythm (SR) group and AF group. The total protein and PKA levels in human atrial tissues were detected by BCA assay and ELISA, respectively. RESULTS：The SK2 channel current densities and the proportion of SK2 channel currents in the integrated inward currents were significantly increased in AF group (all P<0.05 vs SR group). PKA-selective inhibitor H-89 reduced SK2 channel current densities and the proportion of SK2 channel currents in the integrated inward currents in both SR and AF groups, with larger reduction in AF group (all P<0.05 vs SR group). The PKA level was significantly decreased in AF atrial tissues (P<0.05 vs SR group). CONCLUSION: The increase in SK2 channel currents underlies the occurrence and maintenance of AF. PKA-dependent regulation may be involved in the remodeling of SK2 channel in both SR and AF human atrial myocytes, with a more powerful effect in AF.