HCN离子通道对Fontan循环下发生房性心动过速的作用

目的:探讨HCN离子通道对Fontan循环下发生房性心动过速的作用。方法:通过外科手术建立Fontan比格犬模型,术前及术后1周行心脏超声测量右心房大小,穿刺测量右心房和肺动脉压力,行右心房组织病理学检查观察右心房组织的纤维化程度。使用TaqMan实时定量PCR检测右心房肌细胞中HCN2和HCN4 mRNA表达水平,Western blot检测右心房肌细胞中HCN2和HCN4蛋白表达水平,全细胞膜片钳技术检测右心房肌细胞If通道电流。结果:共18只犬进行手术,其中存活5只,Fontan术后存活1周犬右心房内径较术前增加(17.08±1.73)mm对(13.90±1.25)mm,P0.01],右心房压力增高(17.80±2.39)mmHg对(8.40±1.14)mmHg,P0.01],肺动脉压力无明显变化(12.60±2.41)mmHg对(13.00±2.74)mmHg,P0.05]。模型犬右心房组织纤维化程度较对照组增加(P0.05);模型犬术后右心房心肌细胞HCN2和HCN4 mRNA表达水平均较对照组升高(P均0.05),HCN2和HCN4的蛋白表达水平均较对照组升高(P均0.05);HCN通道电流较正常对照组增大,钳制电压为-140 mV时,模型组和对照组电流密度分别为(-1.98±0.14)pA/pF和(-1.09±0.09)pA/pF,P0.01。结论:Fontan循环下心房肌细胞HCN离子通道表达上调,HCN电流增大,可能参与房性心动过速的发生。

Study on the role of HCN channel in the mechanism of atrial tachycardia in Fontan circulation

Objective:To explore the role of HCN channel in the mechanism of atrial tachycardia in Fontan circulation.Methods:The Fontan canine model was created by surgical procedure.Subjected to open-chest study, the size of right atrium, right atrial pressure and pulmonary artery pressure were observed before and 1 week after operation.The fibrosis of right atrium was assessed by histopathology.HCN2 and HCN4 mRNA and protein expression of right atrial myocytes was detected by Taqman real-time RT-PCR and western blot.Whole cell patch-clamp technique was used to detect the If channel current of right atrial myocytes.Results:Eighteen dogs received the operation, and 5 dogs survived from Fontan operation.The atrial diameter (17.08±1.73) mm vs.(13.90±1.25) mm, P<0.01] and right atrial pressure (17.80±2.39) mmHg vs.(8.40±1.14) mmHg, P<0.01] increased in dogs survived 1 week after Fontan operation, while pulmonary artery pressure had no obvious change (12.60±2.41) mmHg vs.(13.00±2.74) mmHg, P>0.05].The right atrial fibrosis of model group was more severe than the control group (P<0.05).The expressions of HCN2 and HCN4 mRNA and protein in right atrial myocytes of model group were higher than those of control group (all P<0.05).The whole cell patch-clamp recording demonstrated that If increased in the model group compared to the control group (-1.98±0.14) pA/pF vs.(-1.09±0.09) pA/pF, HP=-140 mV, P<0.01].Conclusion:Increased If caused by upregulation of HCN channel may promote atrial tachycardia in Fontan circulation.