Apelin regulates the electrophysiological characteristics of atrial myocytes

Backgroud Apelin, a potential agent for treating heart failure, has various ionic effects on ventricular myocytes. However, the effects of apelin on the atrium are not clear. The purpose of this study was to investigate the acute effects of apelin on the electrophysiological characteristics of atrial myocytes. Method Whole-cell patch-clamp techniques were used to investigate the action potential (AP) and ionic currents in isolated rabbit left atrial (LA) myocytes before and after the administration of apelin. Result Apelin reduced LA AP duration measured at 90%, 50% and 20% repolarization of the amplitude by 11 +/- 3%, 24 +/- 5%, 30 +/- 7% at 1 nM (n = 11), and by 14 +/- 4%, 36 +/- 6% and 45 +/- 5% at 10 nM (n = 11), but not at 0.1 nM. Apeline (0.1, 1, 10 nM) did not change the amplitude, or resting membrane potential in LA myocytes. Apelin (1 nM) increased sodium currents, ultra-rapid potassium currents and the reverse mode of sodium-calcium exchanger currents, but decreased late sodium currents and L-type calcium currents and did not change transient outward currents or inward rectifier potassium currents in LA myocytes. Conclusions Apelin significantly changed the atrial electrophysiology with a shortening of AP duration, which may be caused by its effects on multiple ionic currents.