| Objective:To observe the effect of renal sympathetic denervation(RSD)on ventricular arrhythmias(VA),the changes of cardiac structure and function,the expression of cardiac ion channel protein and relevant ion channel currents after myocardial infarction(MI)in rats in an attempt to elucidate the mechanism of RSD on improving ventricular arrhythmias.Methods:Sixty Sprague Dawley rats were randomly divided into three groups:sham,MI(ligation of left anterior descending artery)and MI+RSD(ethanol ablation).Six hours after modeling,electrocardiogram was recorded.Four weeks later,the left ventricular function indexes were obtained through echocardiography,and cardiac tissues were stained by Masson trichrome for fibrotic analysis.The whole-cell patch-clamp was performed to record action potential and transient outward K+ current(Ito).The protein expression of Kv4.2 and Kv4.3 in the left ventricle was detected by using Western blot.Results:The ECG showed ventricular arrhythmias could be significantly induced by MI(p<0.05).Compared with MI group,MI+RSD group could reduced the incidence of PVCs and VT(p<0.05);The echocardiographic showed the MI group had significantly decreased LVEF and FS(p<0.05),and increased LVEDD and LVESD(p<0.05)at 4 weeks after coronary artery ligation compared to that of the sham group.The decline of LVEF and FS was significantly attenuated by the MI+RSD group(p<0.05).The elevation of LVEDD and LVESD was also attenuated by the MI+RSD group(p<0.05);Masson staining showed the area of the collagen fraction was significantly increased in MI group compared with sham groups(p<0.05)and the extent of collagen deposition was attenuated in MI+RSD group compared to MI group(p<0.05);The whole-cell patch-clamp recording showed that MI group had prolonged action potential duration(p<0.05)and mainly prolonged APD50,and the Ito current density was significantly decreased in MI group than that in sham group,and was reversed by RSD.Western immunoblots indicated that the protein expression levels of myocardial Kv4.2 and Kv4.3 were significantly decreased in the MI group compared with sham group(p<0.05).The decline of Kv4.2 protein expression level was significantly attenuated by the RSD treatment(p<0.05).However,RSD treatment had not increased Kv4.3 protein level.Conclusions:RSD reduced the incidence of VA after MI in rats.The mechanism may be that it can reduce the degree of myocardial fibrosis after MI,improve cardiac function and restore the level of Kv4.2 protein expression to inhibit the decrease of Ito current density after MI in rats and then inhibit the prolongation of APD,and thus play a role in anti ventricular arrhythmia. |
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