Objective: To investigate the changes of the two- pore K+ channel TASK-1 in diabetic rats with myocardial injury.
Methods: Thirty-six SD rats were divided into normal group (N), diabetes at 4 weeks (DM 4W) group, and diabetes at 8 weeks (DM 8W) group. The cardiac functions of the rats were determined using cardiac ultrasonography, and the body weight and heart weight of the rats at different time points were measured to calculate the heart/body weight ratio (HW/BW). Myocardial fibrosis in the rats was assessed using Masson's staining. The protein expression of TASK-1 in the myocardium was detected using Western blotting. Whole- cell patch clamp technique was used to record the action potential duration (APD) and twopore domain potassium channel TASK- 1 current in acutely isolated rat ventricular myocytes. meanwhile, The inhibition of TASK-1 current was observed by the TASK-1 specific inhibitor ML-365.
Results: Compared with the normal group, the diabetic rats showed significantly increased HW/BW (P < 0.05), end- diastole left ventricular diameter (LVIDd), end- systolic left ventricular diameter (LVIDs), and TASK-1 protein expression, with obviously decreased left ventricular diameter shortening rate (FS) and ejection fraction (EF) (P < 0.01). Masson staining showed that in diabetic rats, the collagen fibers were thickened, interwoven into a network with uneven arrangement and increased deposition. Compared with DM 4W group, the rats in DM 8W group exhibited progressive increases in LVIDd, LVIDs, HW/BW, and TASK-1 expression (P < 0.01 or 0.05); FS and EF were further decreased (P < 0.01). Masson staining showed worsened morphological changes of the myocardium with increased deposition. Compared with that in the normal group, the current of TASK- 1 in diabetic rats at 8 weeks was significantly reduced (P < 0.01) and the duration of action potential was extended (P < 0.05). The TASK-1 current was successfully inhibited by ML-365.
Conclusions: Diabetes can induce myocardial fibrosis and aggravate myocardial injury possibly in relation to changes in the protein expression and current of the two-port potassium channel TASK-1.
目的: 观察双孔钾通道TASK-1在糖尿病大鼠心肌损伤中的变化并分析其可能机制。
方法: 36只SD大鼠随机分为3组（n= 12/组）：正常对照组（N）、糖尿病4周组（DM 4W）和糖尿病8周组（DM 8W），造模成功后，小动物超声测定各组大鼠心功能；测定不同时期各组大鼠体质量及心脏重量，计算心系数（HW/BW），Masson染色观察心肌纤维化程度，Western blotting检测心肌组织TASK-1的蛋白表达；急性分离N和DM 8W组大鼠心室肌细胞，全细胞膜片钳技术记录其动作电位时程（APD）和TASK-1电流，同时应用TASK-1特异性抑制剂ML-365观察TASK-1电流抑制情况。
结果: 与N组相比，DM组大鼠心系数增加（P < 0.05），大鼠舒张末期左室内径及收缩末期左室内径增加（P < 0.01），TASK-1的蛋白表达增加（P < 0.01），左室内径缩短率及射血分数均下降（P < 0.01），Masson染色显示DM组心肌胶原纤维粗大，交织成网状，排列不均匀，沉积增多；与DM 4W相比，DM 8W组大鼠舒张末期左室内径、收缩末期左室内径、心系数和TASK-1蛋白表达持续增加（P < 0.01，P < 0.05），左室内径缩短率及射血分数进一步下降（P < 0.01），Masson染色显示心肌形态更加不规则，沉积增加明显。与N组相比，DM 8W糖尿病心肌病组TASK-1的电流明显减少（P < 0.01），动作电位时程延长（P < 0.05），TASK-1电流被ML-365成功抑制。
结论: 糖尿病可诱发心肌纤维化，加重心肌损伤，其机制可能与双孔钾通道TASK-1的蛋白及电流变化有关。
Keywords: TASK-1; diabetes mellitus; myocardial injury; two-port potassium channel.