Abstract: Objective:To investigate the sarcoplasmic reticulum Ca²⁺-ATPase(SERCA) activity and mRNA expression in rat heart in infrarenal abdominal aorta occlusion induced ischemia and reperfusion injury(I/R).Methods:Forty male Sprague-Dawley rats were randomized into five groups:pseudo-operation group,I/R2h group,I/R12h group,I/R24h group and I/R48h group.Rats in pseudo-operation group were undergone laparotomy only.Meanwhile,rats in I/R groups were reperfused with different hours (2,12,24 and 48 hours) following by 30 minutes infrarenal abdominal aorta occlusion induced ischemia.Then the rat hearts in each group were obtained at the specified time points.The activity of SERCA was determined by inorganic phosphorus colorimetry,and gene expression of SERCA was analyzed by reverse transcriptional-PCR.Results:Compared with the pseudo-operation group,the levels of SERCA activity and gene expression in I/R24h group and I/R48h group were down-regulated significantly(P<0.01);but in I/R12h group,SERCA activity was decreased,while gene expression had no statistical difference.And there were no statistical significance about SERCA activity and gene expression in rat heart between the I/R2h group and pseudo-operation group(P>0.05).Conclusions:Infrarenal abdominal aorta occlusion may obviously affect the activity and gene expression of SERCA in rat heart.