Western blotting
Left atrial tissues were collected after isolated heart perfusion, and were homogenized using a tissue lyser. Levels of RyR2 (ryanodine receptor, LS-C93425, LifeSpan BioSciences, USA), SERCA2 (sarcoplasmic reticulum calcium pump, 4388s, Cell Signaling Technology, USA) and NCX1 (Na+/Ca2+ exchanger, 5507-I-AP, Proteintech, USA) were determined by western blotting as our previous study 13.