Modulation of canine cardiac sodium current by Apelin

Apelin, a ligand of the G protein-coupled putative angiotensin II-like receptor (APJ-R), exerts strong vasodilating, cardiac inotropic and chronotropic actions. Its expression is highly up-regulated during heart failure. Apelin also increases cardiac conduction speed and excitability. While our knowledge of apelin cardiovascular actions is growing, our understanding of the physiological mechanisms behind the cardiac effects remains limited. We tested the effects of apelin on the cardiac sodium current (INa) using patch clamp technique on cardiac myocytes acutely dissociated from dog ventricle. We found that apelin-13 and apelin-17 increased peak INa by 39% and 61% and shifted its mid-activation potential by − 6.8 ± 0.6 mV and − 17 ± 1 mV respectively thus increasing channel opening at negative voltage. Apelin also slowed INa recovery from inactivation. The effects of apelin on INa amplitude were linked to activation of protein kinase C. Apelin also increased INa “window” current by up to 600% suggesting that changes in intracellular sodium may contribute to the apelin inotropic effects. Our results reveal for the first time the effects of apelin on INa. These effects are likely to modulate cardiac conduction and excitability and may have beneficial antiarrhythmic action in sodium chanelopathies such as Brugada Syndrome where INa amplitude is reduced.