Electrophysiological effects of amiodarone on pacemaker cells in guineapig left ventricular outflow tract under conditions of hypoxia,acidosis and treatment with epinephrine / 中国病理生理杂志

ABSTRACT

AIM:To study the electrophysiological effects of amiodarone on the pacemaker cells in guinea-pig left ventricular outflow tract under the conditions of hypoxia,acidosis and treatment with epinephrine.METHODS:The action potentials of the pacemaker cells in guinea-pig left ventricular outflow tract were recorded by conventional intracellular microelectrode technique.The effects of amiodarone on the spontaneous slow response potentials were investigated under the conditions of hypoxia,acidosis and treatment with epinephrine.RESULTS:(1) Amiodarone at concentration of 0.1 ?mol/L markedly decreased the rate of pacemaker firing (RPF) and maximal diastolic potential (MDP),lengthened 80% of the duration of action potential (APD80).Amiodarone at concentration of 1 ?mol/L significantly decreased the velocity of diastolic depolarization (VDD) and RPF,the maximal rate of depolarization (Vmax),MDP and amplitude of action potential (APA),lengthened 50% of the duration of action potential (APD50) and APD80.Amiodarone at concentration of 10 ?mol/L led to a significant decrease in VDD and RPF,Vmax,MDP and APA,a notable lengthening in APD50 and APD80 was also observed.(2) Under the condition of hypoxia and perfusion with deprived glucose content for 15 min,VDD,RPF,MDP,Vmax and APA decreased significantly,APD50 was shortened notably.Under the condition of hypoxia,amiodarone at concentration of 1 ?mol/L significantly decreased VDD,RPF and Vmax,increased MDP,lengthened APD50 and APD80 as compared to the cells treated with hypoxia only.(3) Perfusion with pH 6.8 solution for 10 min,VDD and RPF significantly decreased,Vmax and APA notably reduced,APD80 was markedly shortened.Under the condition of acidosis for 10 min,amiodarone significantly decreased VDD,RPF,MDP and APA,lengthened APD50 and APD80 as compared to the cells under the condition of acidosis only.(4) Perfusion of epinephrine at concentration of 10 ?mol/L for 10 min resulted in a significant increase in VDD,RPF,Vmax,MDP and APA,a notable shorting in APD50 and APD80 was also observed.Compared to 10 ?mol/L epinephrine group,1 ?mol/L amiodarone+ 10 ?mol/L epinephrine significantly reduced VDD,RPF,Vmax,MDP and APA,lengthened APD50 and APD80.CONCLUSION:Amiodarone markedly decreases the autorhythmicity of the pacemaker cells in guinea-pig left ventricular outflow tract.This electrophysiological effects were significantly influenced by hypoxia,acidosis and epinephrine.