Abstract: 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.

Key words: Baicalin, heart failure, endoplasmic reticulum stress, apoptosis, isolated heart preparation, myoelectric stability of ventricular myocytes