Background: Ca²⁺ plays important role of myocardial contractility and arrhythmogenesis. There were many studies about ventricular calcium regulatory process in heart failure(HF). Down-regulation of sarcoplasmic reticulum Ca²⁺-ATPase(SERCA) and ryanodine receptor 2(RyR2) are major causes of decreased contractility and arrhythmogensis in ventricular tissue. But there are very few studies about calcium handling process in HF atrial tissue. Because incidence of HF and atrial fibrillation(AF) are increased progressively. It is necessary to evaluate regulation of calcium handling in HF atrial tissue. Increased angiotensin II level was noted in HF. Angiotensin II can induce endothelin production. So, we can expect, there are correlation between endothelin and AF in HF. Because of that, we evaluated gene expression of sarcoplasmic reticulum calcium regulatory protein; SERCA, phospholamban(PLB), RyR2 and endothelin system; endothelin-1(ET1), ETA receptor(ETa), ETB receptor(ETb). Method: Rats myocardial infarction were made by left anterior descending artery ligation. 8 weeks after MI, isoproterenol were administrated for 2weeks by osmotic pump (30���/���/hr).Cardiac function were assessed by echo and left atrial appendage tissues were obtained to do real time PCR study. Result: 5 Post MI + isoproterenol infusion rats and 5 control rats were used. Left ventricular end-diastolic dimension (LVEDD) was increased (0.56짹0.03 vs 0.82짹0.04cm p<0.01), LV ejection faction was significantly decreased (88.5짹2.9 vs 41.9짹10.7%, p<0.01). In HF atrial tissue, mRNA level of SERCA, PLB, RyR2 were decreased significantly (normalized ratio(NR) SERCA 0.13짹0.03, p<0.001. PLB 0.44짹0.17, p<0.05. RyR2 0.29짹0.06, p<0.001). PLB/SERCA ratio was increased (4.5짹2.7). ET1, ETa mRNA levels were slightly increased (NR ET1 1.71짹0.52, p=0.2; ETa 1.25짹0.30, p=0.4). But ETb was significantly increased in HF (NR 1.55짹0.24, p<0.05) Conclusion: In atrial tissue of rat HF model, mRNA level of SERCA, RyR2 were decreased and PLB/SERCA was increased. These findings are important for understanding of atrial arrhythmic mechanism and atrial contractile dysfunction in HF.