Reher Thomas A, Wang Zhuo, Hsueh Chia-Hsiang, Chang Po-Cheng, Pan Zhenwei, Kumar Mohineesh, Patel Jheel, Tan Jian, Shen Changyu, Chen Zhenhui, Fishbein Michael C, Rubart Michael, Boyden Penelope, Chen Peng-Sheng
The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN.
Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, China.
J Am Heart Assoc. 2017 May 26;6(6):e005471. doi: 10.1161/JAHA.117.005471.
Purkinje cells (PCs) are important in cardiac arrhythmogenesis. Whether small-conductance calcium-activated potassium (SK) channels are present in PCs remains unclear. We tested the hypotheses that subtype 2 SK (SK2) channel proteins and apamin-sensitive SK currents are abundantly present in PCs.
We studied 25 normal rabbit ventricles, including 13 patch-clamp studies, 4 for Western blotting, and 8 for immunohistochemical staining. Transmembrane action potentials were recorded in current-clamp mode using the perforated-patch technique. For PCs, the apamin (100 nmol/L) significantly prolonged action potential duration measured to 80% repolarization by an average of 10.4 ms (95% CI, 0.11-20.72) (n=9, =0.047). Voltage-clamp study showed that apamin-sensitive SK current density was significantly larger in PCs compared with ventricular myocytes at potentials ≥0 mV. Western blotting of SK2 expression showed that the SK2 protein expression in the midmyocardium was 58% (=0.028) and the epicardium was 50% (=0.018) of that in the pseudotendons. Immunostaining of SK2 protein showed that PCs stained stronger than ventricular myocytes. Confocal microscope study showed SK2 protein was distributed to the periphery of the PCs.
SK2 proteins are more abundantly present in the PCs than in the ventricular myocytes of normal rabbit ventricles. Apamin-sensitive SK current is important in ventricular repolarization of normal PCs.
浦肯野细胞（PCs）在心律失常的发生中起重要作用。小电导钙激活钾（SK）通道是否存在于PCs中仍不清楚。我们检验了以下假设：2型SK（SK2）通道蛋白和蜂毒明肽敏感的SK电流大量存在于PCs中。
我们研究了25个正常兔心室，包括13个膜片钳研究、4个用于蛋白质免疫印迹分析以及8个用于免疫组织化学染色。使用穿孔膜片技术在电流钳模式下记录跨膜动作电位。对于PCs，蜂毒明肽（100 nmol/L）显著延长动作电位时程，以复极化至80%时测量，平均延长10.4 ms（95% CI，0.11 - 20.72）（n = 9，P = 0.047）。电压钳研究表明，在电位≥0 mV时，与心室肌细胞相比，PCs中蜂毒明肽敏感的SK电流密度显著更大。SK2表达的蛋白质免疫印迹分析显示，中层心肌中SK2蛋白表达量是假腱索中的58%（P = 0.028），心外膜中是50%（P = 0.018）。SK2蛋白免疫染色显示，PCs染色比心室肌细胞更强。共聚焦显微镜研究显示SK2蛋白分布于PCs的周边。
正常兔心室的PCs中SK2蛋白比心室肌细胞中更丰富。蜂毒明肽敏感的SK电流在正常PCs的心室复极化中起重要作用。
