Study on protection of a Shenfu injection against myocardial ischemia-reperfusion arrhythmias in aged mice

Objective To investigate the protective effects of pretreatment with a Shenfu(SF)injection on arrhythmias induced by myocardial ischemia-reperfusion(IR)injury in aged mice. Methods Thirty 18-month-old C57BL/6J mice were randomly divided into 3 groups(n=10, each group): the sham treatment group(receiving sham operation without thoracotomy), the IR group(undergoing the ligation of the left anterior descending coronary artery with ischemia for 30 min and reperfusion for 2 h)and the SF group(receiving SF intraperitoneal injection of 10 ml/kg 30 min before thoracotomy and the same treatment as the IR group). Arrhythmias were monitored, and serum levels of creatine kinase-isoenzyme(CK-MB), troponin(cTnI)and tumor necrosis factor α(TNFα), and the ratio of myocardial connexin 43(Cx43)phosphorylation(ser368)to total protein(p-Cx43/t-Cx43)were detected in the three groups. Results Ventricular arrhythmias occurred in the IR and SF groups.Compared with the IR group, ventricular arrhythmias in the SF group were alleviated, the frequency of ventricular premature systolic episodes was reduced(36.6±13.5 times vs. 48.4±22.1 times), the frequency of ventricular tachycardia/fibrillation decreased(3.4±1.8 times vs. 7.6±3.5 times), and the total duration of ventricular tachycardia/fibrillation episodes was shortened(8.9±4.5 times vs. 17.7±5.1 times)in the SF group(P 0.05)between the two groups.Compared with the sham treatment group, serum levels of CK-MB, cTnI and myocardial TNF(increased in the IR and SF groups(P<0.05), and their levels were lower in the SF group than in the IR group(P<0.05). Compared with the sham treatment group, the ratio of Cx43 ser368/total protein was lower in the IR and SF groups, but was higher in the SF group than in the IR group(P<0.05). Conclusions SF pretreatment can significantly reduce IR-induced arrhythmias in aged mice possibly by reducing TNF(and up-regulating the phosphorylation activity of Cx43. Key words: Shenfu injection; Arrhythmias, cardiac; Myocardial reperfusion; Connexins