Discrepant electrophysiological characteristics and calcium homeostasis of left atrial anterior and posterior myocytes

The left atrial (LA) posterior wall has been demonstrated to have regional electrophysiological differences with a higher arrhythmogenic potential leading to atrial fibrillation (AF). However, the ionic characteristics and calcium regulation in the LA anterior and posterior myocytes have not been fully elucidated. The purpose of this study was to investigate the electrical characteristics of the LA anterior and posterior myocytes. Whole-cell patch-clamp techniques and the indo-1 fluorimetric ratio technique were used to investigate the characteristics of the ionic currents, action potentials, and intracellular calcium in single isolated rabbit myocytes in the LA anterior and posterior walls. The expression of the Na + –Ca 2+ exchanger (NCX) and ryanodine receptor (RyR) were evaluated by a Western blot. The LA posterior myocytes ( n = 15) had a higher incidence (53 vs. 19%, P