Effects of ANP on pulmonary vein electrophysiology, Ca²⁺ homeostasis and adrenergic arrhythmogenesis via PKA

Atrial fibrillation (AF) is the most common form of arrhythmia and increases the risk of stroke and heart failure (HF). Pulmonary veins (PVs) are important sources of triggers that generate AF, and calcium (Ca²⁺) overload participates in PV arrhythmogenesis. Neurohormonal activation is an important cause of AF. Higher atrial natriuretic peptide (ANP) level predicts paroxysmal AF occurrence in HF patients. However, it is not clear if ANP directly modulates electrophysiological characteristics and Ca²⁺ homeostasis in the PVs. Conventional microelectrodes, whole-cell patch-clamp, and the Fluo-3 fluorimetric ratio technique were performed using isolated rabbit PV preparations or single isolated PV cardiomyocytes before and after ANP administration. We found that ANP (1, 10, and 100 nmol/L) concentration-dependently decreased spontaneous activity in PV preparations. ANP (100 nmol/L) decreased isoproterenol (1 μmol/L)-induced PV spontaneous activity and burst firing. AP811 (100 nmol/L, NPR-C agonist), H89 (1μmol/L, PKA inhibitor) decreased isoproterenol-induced PV spontaneous activity or burst firing, but successive administration of ANP had no further effect on PV activity. KT5823 (1 μmol/L, PKG inhibitor) decreased isoproterenol-induced PV spontaneous activity but did not change isoproterenol-induced PV burst firing, whereas successive administration of ANP did not change isoproterenol-induced PV burst firing. ANP decreased intracellular Ca²⁺ transient and sarcoplasmic reticulum Ca²⁺ content in single PV cardiomyocytes. ANP decreased the late sodium current, L-type Ca²⁺ current, but did not change nickel-sensitive Na⁺-Ca²⁺ exchanger current in single PV cardiomyocytes. In conclusion, ANP directly regulates PV electrophysiological characteristics and Ca²⁺ homeostasis and attenuates isoproterenol-induced arrhythmogenesis through NPR-C/cAMP/PKA signal pathway.