Effects of l-carnitine on action potential of canine papillary muscle during hypoxic perfusion

Under hypoxic (95% N2 + 5% CO2) perfusion, electrophysiological effects of L-carnitine on canine papillary muscles were studied using standard microelectrode techniques. During hypoxic perfusion for 60 min, resting membrane potential (RMP), action potential amplitude (APA) and maximum upstroke velocity of phase 0 were decreased, and action potential duration (APD) and effective refractory period (ERP) were shortened. Application of L-carnitine 25 mM under hypoxic perfusion increased RMP and APA and prolonged APD and ERP significantly. As effects of L-carnitine during hypoxic perfusion might be that of hypertonicity, effects of sucrose of the same tonicity as L-carnitine were studied under hypoxia. Sucrose did not cause significant changes on various parameters of action potential compared with hypoxic perfusion. It was suggested that the increase in RMP, and the prolongation of APD and ERP might be caused by an increase in intracellular ATP content. The findings in this study could be an explanation of possible antiarrhythmic effects of L-carnitine.