RYR2 and atrial fibrillation: Since phosphorylation of most Ca2+-handling proteins is altered in many models of experimental HF and AF, which might lead to increased Ca2+ release from the sarcoplasmic reticulumn and disruption of Ca2+ homeostasis, we examined the effects of vidarabine and V2E on protein kinase A-dependent ryanodine receptor 2 (RyR2) phosphorylation (Ser-2808).