RESUMEN
Objective To investigate the effects of Tanshinone Ⅱ A (extracted from Chinese herb medicine Salvia miltiorrhiza Bge.) on ventricular arrhythmias of rabbit hearts induced by ischemia in order to illuminate its mechanism of anti-arrhythmia.Methods Thirty rabbits were randomly (random number)divided into normal group,ischemic group and Tanshinone Ⅱ A group.Model of wedge shaped mass of rabbit left ventricular myocardium with coronary perfusion was prepared,and then by using floating glassy microelectrode,the trans-mural ECG,QT interval,the trans-mural dispersion of re-polarization (TDR) and trans-membrane action potentials from both endocardium and epicardium were simultaneously and wholly recorded.The incidence of ventricular arrhythmia in myocardium was observed after ischemia for thirty min.Results Under the condition of acute ischemia,compared with normal group,the incidence of ventricular arrhythmia and TDR were significantly increased in ischemia group (P ＜ 0.01),while incidence of ventricular arrhythmia and TDR were significantly reduced in tanshinone ⅡA group compared with ischemia group (P ＜ 0.05).The incidences of ventricular arrhythmia in normal,ischemia and Tanshinone Ⅱ A groups were 0/10,9/10 and 2/10 respectively.Conclusions Tanshinone Ⅱ A prevents ventricular arrhythmia and reduces TDR significantly in ischemic rabbit hearts.
RESUMEN
Objective To determine the effect of calmodulin-dependent kinase Ⅱ (CaMK Ⅱ ) -ryanodinereceptor pathway signaling in rabbits with left ventricular bypertrophy (LVH) and triggered ventricular arrhythmia.Methods Forty New Zealand rabbits were randomized into four groups ( n =10 per group):the sham operation group,LVH group,KN-93 (CaMKⅡ inhibitor) group (LVH + KN-93),and the ryanodinegroup ( LVH + ryanodine).Rabbits in the LVH,KN-93,and ryanodinegroups were used to establish a left ventricular hypertrophy model by the coarctation of the abdominal aorta,while the rabbits in the sham operation group did not have the coarctation.After eight weeks,action potentials (APs) were recorded simultaneously in the endocardium and epicardium,and transmural electrocardiogram (ECG) was also recorded in the wedge shaped models of rabbits' left ventricular myocardium.Drugs were administered to animals in the KN-93 and ryanodinegroups respectively,and the frequency of triggered APs and ventricular tachycardia were recorded after isoprenaline ( 1 μmol/L),and high-frequency electrical stimulation were given to rabbits.Results The incidences (animals/group) of triggered APs were:sham,0/10 ; LVH,10/10; KN-93,4/10; and ryanodine,1/10.The incidences of ventricular tachycardia induced were 0/10,9/10,3/10,and 1/10,respectively.The incidences of triggered ventricular arrhythmias in the KN-93 group and ryanodine groups tachycardia or ventricular fibrillation were 0/10,7/10,2/10,and 1/10,respectively.The incidences of triggered ventricular arrhythmias in the KN-93 group and ryanodine groups were much lower than that in the LVH group (P ＜ 0.05).Conclusions KN-93 and ryanodinecan effectively reduce the occurrence of triggered ventricular arrhythmia in rabbits with LVH.The CaMK Ⅱ-ryanodine signaling pathway can be used as a novel target site of treating ventricular arrhythmia.