The Effects Of Cilostazol And Fluvastatin On The Transient Outward Potassium Current And L-Type Calcium Channels In Rat Right Ventricular Myocyte

Backgroud:Brugada syndrome (BrS) is the hereditary disease involving cardiac electrical activity disorder. It ofen occurs in the normal cardiac structure of male young people, and is one of the main reasons for the sudden cardiac death of the young crowd. The first symptom of BrS is often syncope or even sudden death, and seizures without aura; the incidence in Asia is significantly higher than in Europe, it is also known as "Southeast Asia sudden unexplained nocturnal death syndrome". It is imminent how to effectively prevent and further treatment the rapid ventricular arrhythmias, ventricular fibrillation (VF) or sudden cardiac death of BrS. At present, most scholars believe that phase2reentry mediated by transient outward potassium current(Ito) is the main mechanism of BrS arrhythmia. In addition, L-calcium current (Ica,L) is also importantion basis. Implantable cardioverter-defibrillator (ICD) is recognized as the only effective means that can prevent malignant ventricular arrhythmia of BrS. However, ICD has many defects, for example, high defibrillation threshold, false discharge, expensive. Hence,drug treatment is still the main research direction for BrS, especially the drugs with the high selectivity of the heart and specific inhibitor of Ito. Cilostazol, a phosphodiesterase III inhibitor, is usually an anti-platelet aggregation drug and commonly used in clinical chronic arterial occlusion. In recent years, a number of studies have shown that cilostazol can also regulate lipids, inhibit intimal hyperplasia of artery, prevent thrombosis and vascular restenosis after percutaneous coronary intervention treatment. It also has anti-arrhythmia effect. It is still controversial that the ion channel mechanisms that cilostazol prevent tachyarrhythmias. Statins are widely used in cardiovascular disease and have pleiotropic effects. They regulate lipids mainly, and also improve the funtion of vascular endothelial, stabilize and reverse the atherosclerotic plaque. In recent years, the role of non-regulation of blood lipids increasingly received attention of clinician. In this study, we used the whole cell patch clamp recording techniques to study the effects of different concentrations of cilostazol and fluvastain sustained release tablets for Ito and Ica,L which distribute rat right ventricular myocytes.Objective:This study aims to observe the effects of Cilostazol and fluvastain on the transient outward potassium current and L-Type Calcium Channels in rat right ventricular myocyte, explore the mechanism of ion channels that ciolstazol inhibit ventricular arrhythmias in BrS and have a preliminary understanding that wether fluvastain sustained release tablets can prevent ventricular arrhythmias in BrS.Methods:Single myocytes were isolated from right ventricular of adult rat with collagenase Ⅱ. Ito and Ica,L in cell of right ventricular were recoreded by whole-cell patch clamp technique. This experiment were divided into two parts,(1) acute pharmacological expriment means the perfusion expriment:ionic currents were recorded after5min of equilibration with normal extracellular solution for control data, and then recorded following2min of perfusion with cilostazol;(2) chronic pharmacological expriment means oral medication expriment. In perfusion expriment, there are four groups, Cilostazole1μmol/L, Cilostazole2μmol/L, Cilostazole5μmol/L, Cilostazole50μmol/L. The differentce about current density of Ito was recoreded between before and after drug perfusion in each group, and The differentce about change of current density of Ito also was observed among four groups. In oral medication expriment, the oral cilostazol expriment included two groups, control group(CON group) and exprimental group(CILO group), the rats were given lOmg/kg/d cilostazol and fed four weeks in CILO group, then The differentce about current density of Ica.L was recoreded between the two groups; the oral fluvastain expriment also included two groups, controll group(CON1group) and exprimental group(FVT group), the rats also were given8mg/kg/d fluvastatin and fed four weeks in FVT group, then the differentce about current density of Ito was recoreded between the two groups.Results:1、 The result of perfusion expriment (1)the differentce about current density of Ito between before and after cilostazol perfusion:①the differentce about current density of Ito between before and after Cilostazole lμmol/L perfusion, in most of the command voltage, current density of Ito after cilostazol perfusion is lower than before, and there were significant statistical differences from0mV to+60mV;②the differentce about current density of Ito between before and after Cilostazole2μmol/L perfusion, in most of the command voltage, current density of Ito after cilostazol perfusion is lower than before, and there were statistical differences from +30mV to+60mV;③the differentce about current density of Ito between before and after Cilostazole5μmol/L perfusion, in most of the command voltage, current density of Ito after cilostazol perfusion is lower than before, and there were statistical differences from0mV to+60mV;④the differentce about current density of Ito between before and after Cilostazole50μmol/L perfusion, in most of the command voltage, current density of Ito after cilostazol perfusion is lower than before, and there were statistical differences from+20mV to+60mV;(2)the comparison about the reduction rate of current density of Ito among four groups:in the command voltage, this study compared the reduction rate of current density of Ito among four different concentrations of cilostazol perfusate, and found there was no significant changes among four groups without statistical significance(P>0.05), in addition, reduction rate of current density of Ito are all about60%among four groups in+60mV.2、 The result of oral medication expriment (1)the change in current density of Ica.L between before and after oral cilostazol:there is no change between CON group and CILO group without statistical significance(P>0.05) from-50mV to+60mV.(2)the change in current density of Ito between before and after oral fluvastatin:there is no change between CON1group and FVT group without statistical significance(P>0.05) from-50mv to+60mV.Conclusions:1. Ito was significantly inhited when Cilostazole lμmol/L, Cilostazole2μmol/L, Cilostazole5μmol/L, Cilostazole50μmol/L directly acted on the rat right ventricular cells, there was no difference in the degree of decline of Ito from Cilostazole1μmol/L to Cilostazole50μmol/L; It is the "all or non"direct effect of ion channel that cilostazol inhibites Ito.2. oral cilostazol had no effect for Ica.1. in the rat right ventricular cells;3. oral fluvastatin had no effect for Ito in the rat right ventricular cells.