黄芩苷对心力衰竭大鼠心律失常及心室肌细胞内质网应激-肌电稳定性的影响

目的　探究黄芩苷对心力衰竭大鼠室性心律失常及心室肌细胞内质网应激-肌电稳定性的影响。方法　雄性6周龄Wistar大鼠72只，随机分为对照组，模型组，美托洛尔组，黄芩苷低、中、高剂量组，每组12只。模型组给予异丙肾上腺素（ISO）后颈部皮下注射5 mg/（kg·d），对照组给予等体积0.9%NaCl注射液后颈部皮下注射，连续注射7 d；美托洛尔组及黄芩苷低、中、高剂量组在模型组基础上分别给予美托洛尔10 mg/（kg·d）及25、50、100 mg/（kg·d）黄芩苷灌胃，对照组给予药物等体积0.9%NaCl注射液灌胃，连续给药4周。于4周末行心电图及多普勒超声检测各组大鼠心率、室性早搏发生情况及测定左心室射血分数（LVEF）、左心室舒张末期内径（LVEDd）、左心室收缩末期内径（LVESd）；酶联免疫吸附测定（ELISA）法检测各组大鼠血清人基质裂解素2（ST2）、脑钠肽（BNP）含量。每组取6只大鼠制备Langendorff离体心脏灌注模型，记录和测量心肌单相动作电位复极90%的时程（MAPD90）、心室肌细胞有效不应期（ERP）及ERP/MAPD90比值；另外6只大鼠行心室肌TUNEL染色后检测其心肌细胞凋亡情况；Western blot检测各组大鼠心室肌细胞葡萄糖调节蛋白78（GRP78）、肌醇需酶1（IRE1）、C/EBP环磷酸腺苷反应元件结合转录因子同源蛋白（CHOP）及缝隙连接蛋白43（Cx43）蛋白表达。结果　与对照组比较，模型组大鼠心率增快，易发生室性早搏，LVESd、LVEDd升高，LVEF降低，血清ST2、BNP含量升高，心室肌细胞ERP/MAPD90降低，凋亡指数（AI）升高，GRP78、IRE1、CHOP表达升高，Cx43表达降低（均P＜0.05）；与模型组比较，黄芩苷低、中、高剂量组上述指标均明显改善，且呈剂量依赖性（P＜0.05）。结论　黄芩苷具有改善ISO所致心力衰竭大鼠室性心律失常及心功能的作用，其机制可能与抑制心室肌细胞内质网应激及细胞凋亡、提高肌电稳定性相关。

Effects of baicalin on arrhythmia and endoplasmic reticulum stress EMG stability of ventricular myocytes in rats with heart failure

Objective　To investigate the effect of baicalin on arrhythmia and endoplasmic reticulum stress EMG stability of ventricular myocytes in rats with heart failure. Methods　Seventy-two male Wistar rats (6 weeks) were randomly divided into control group, model group, baicalin group and metoprolol group, with 12 rats in each group. The model group was given isoproterenol (ISO) subcutaneous injection of 5 mg/(kg·d), and the control group was given equal volume of 0.9% NaCl injection subcutaneously in the posterior neck for 7 days. Baicalin low, medium and high dose groups and metoprolol group were given baicalin 25, 50 and 100 mg/(kg·d)] and metoprolol 10 mg/(kg·d) respectively on the basis of the model group, while the control group was given the same volume of 0.9% NaCl injection for 4 weeks. At the end of 4 weeks, ECG and Doppler ultrasound were used to detect heart rate, incidence of premature ventricular contractions, left ventricular ejection fraction (LVEF), left ventricular end diastolic diameter (LVEDd) and left ventricular end systolic diameter (LVESd). Serum levels of ST2 and BNP were detected by ELISA. The isolated Langendorff heart perfusion model was made by 6 rats in each group. The 90% time course of monophasic action potential (MAPD90), effective refractory period (ERP) of ventricular myocytes and the ratio of ERP / MAPD90 were recorded and measured. TUNEL staining was used to detect the apoptosis of ventricular myocytes. Western blot assay was used to detect the expression levels of Cx43, GRP78, IRE1 and CHOP protein. Results　Compared with the control group, the heart rate increased, LVESd and LVEDd increased, LVEF decreased, serum levels of ST2, BNP increased, ERP / MAPD90 decreased, AI value increased, GRP78, IRE1, CHOP expression increased and Cx43 expression decreased in the model group (all P＜0.05). Compared with the model group, the above indexes were significantly improved in baicalin low, medium and high dose groups, and showed a dose-dependent pattern (P＜0.05). Conclusion　Baicalin can improve ventricular arrhythmia and cardiac function in rats with heart failure induced by ISO. The mechanism may be related to the inhibition of endoplasmic reticulum stress apoptosis and the improvement of EMG stability.