Effects Of Varied Electrophysiological Parameters With Pinacidil Preconditioning On Ventricular Myocardium During Ischemia And Reperfusion In Rabbits

Objective: To investigate the effects of varied electrophysiological parameters with different concentration of pinacidil preconditioning on ventricular myocardium during ischemia and reperfusion period in rabbits.Methods: 32 anesthetized rabbits were randomly assigned into four groups: Saline+ ischemic reperfusion (IR) group (n=8); Pinacidil (0.2mg/kg or 0.4mg/kg or 0.8mg/kg) preconditioning + IR group, (n=8, respectively). Saline or pinacidil was injected intravenously before ten minutes of left anterior descending coronary artery (LAD) ligation in rabbits. Varied parameters of monophasic action potentials (MAPs) were recorded by monophasic action potentials techquie in vivo and S1-S2 programmed electrical stimulation (PES) method was employed to measure Ventricular fibrillation threshold (VFT) and ventricular vulnerable period (VVP).Results: 1. (1) MAPD90 and MAPD50 decreased immediately after pinacidil was given; Compared with that in control group, MAPD90 and MAPD50 of ischemia zone in pinacidil(0.8mg/kg) precontioning group were shortened by 15.4% and 31% after ischemia 30 minutes (P<0.05, respectively). (2) The pinacidil (0.2mg/kg,0.4mg/kg and 0.8mg/kg) preconditioning group can eliminate early afterdepolarization(EAD) on ventricular myocardium during ischemia and reperfusion period. (3) Compared with control group, pinacidil (0.2mg/kg) precontioning group could significantly decrease MAPD90d and MAPD50d between ischemic zone and no-ischemic zone during ischemia and reperfusion period (P<0.05); Pinacidil (0.8mg/kg) precontioning group could significantly increase MAPD90d and MAPD50d in contrast with pinacidil (0.2mg/kg) precontioning group (P<0.05).2. (1) Compared with control group, pinacidil (0.2mg/kg) preconditioning group could increase VFT and shorten VVP during ischemia and reperfusion period (P<0.05). (2)There was not statistically significant difference on VFT and VVP between pinacidil (0.8mg/kg) preconditioning group and control group during ischemia or reperfusion period (P>0.05). (3)Pinacidil (0.8mg/kg) preconditioning group can decrease VFT and prolong VVP compared with pinacidil (0.2mg/kg) preconditioning group (P<0.05).Conclusion: (1) The ischemia or reperfusion arrhythmias could be suppressed by pinacidil preconditioning and mechanism may relate to eliminate early afterdepolarization (EAD). (2) The higher concentration of pinacidil preconditioning trended to promote reentrant arrhythmia by shortened MAPD during ischemia period. (3) Dual characters of ATP-sensitive potassium channels opener on ischemia or reperfusion arrhythmia maybe have a relation with concentration -dependence.