Abstract： Objective To investigate changes in the expression of sarcoplamic reticular Ca2+-A TPase (SERCA) and IP3-I receptors (IP3R1) mRNA in patients with atrial f ibrillation.Methods Thirty-eight patients with mitral stenosis undergoing open heart surgery were s tudied. 100 mg of atrial tissue was obtained during surgery from the right app endage and the right atrium. The amount of messenger ribonucleic acid (mRNA) am ount of SERCA and IP3R1 was measured by reverse transcription-polymerase ch ain reaction (RT-PCR) and normalized to the mRNA levels of glyceraldehyde 3-ph osphate dehydrogenase (GAPDH). Results Levels of mRNA expression of SERCA in patients with AF, as compared with subjec ts in sinus rhythm, was lower and that of IP3R1 was higher. The longer AF w as sustained, the higher the levels of mRNA. There was no significant differenc e between right atrial free wall and right appendage.Conclusions The expression changes of SERCA and IP3R mRNA may correlate with the initiation or maintenance of AF.