Relationship between CaMK II and levosimendan against arrhythmia induced by myocardial ischemia-reperfusion in rats in vitro

Abstract

Objective To evaluate the relationship between calmodulin protein kinase Ⅱ (CaMK Ⅱ) and levosimendan against arrhythmias induced by myocardial ischemia-reperfusion (I/R) in rats in vitro.Methods Thirty male Wistar rats,weighing 250-300 g,were randomly divided into 3 groups (n =10 each) using a random number table:control group (group C),I/R group and levosimendan group (group L).Their hearts were rapidly excised and perfused in a langendorff apparatus with K-H solution saturated with 95％ O2-5％ CO2 at 36.5-37.5 ℃.At 20 min of equilibration,the hearts were perfused with K-H solution for 60 min in group C.The hearts were subjected to 30 min of ischemia followed by 30 min reperfusion with K-H solution in group I/R.The hearts were subjected to 30 min of ischemia followed by 30 min reperfusion with K-H solution containing 300 nmol/L levosimendan in group L.Left ventricle developed pressure (LVDP),left ventricle end-diastolic pressure (LVEDP),+ dP/dt-dP/dtmax and heart rate (HR) were recorded immediately before ischemia and at 15 and 30 min of reperfusion.Arrhythmia was recorded during reperfusion and scored.Specimens were obtained from the apex of heart at 30 min of reperfusion for determination of the intracellular calcium concentration ([Ca2 +] i).Myocardial specimens were obtained from the left ventricle at 30 min of reperfusion to detect CaMK Ⅱ activity.Results Compared with group C,arrhythmia score,[Ca2+]i and CaMK [Ⅱ activity were significantly increased,and LVDP,+ dP/dtmax,-dP/dtmax and HR were decreased,and LVEDP was increased at 15 and 30 min of reperfusion in group I/R.Compared with group I/R,the number of ventricular premature beat,arrhythmia score,[Ca2+] i and CaMK Ⅱ activity were significantly decreased,and LVDP,+ dP/dtmax,-dP/dtmax and HR were increased,and LVEDP was decreased at 15 and 30 min of reperfusion in group L.Conclusion Inhibition of CaMK Ⅱ activity is involved in the mechanism by which levosimendan decreases the development of arrhythmias induced by myocardial I/R in rats. Key words: Calcium-calmodulin-dependent protein kinase type 2; Pyridazines; Myocardial reperfusion injury; Arrhythmias, cardiac