Abstract： Objective To investigate the effect of altered mRNA expression of sarcolemmal calcium transporting channel proteins in rat myocardial ischemia reperfusion injury (IR)in vivo on calcium overload.Methods Twelve SD rats were randomized into IR and control groups. LAD coronary artery was ligated for 20 min (ischemia) then released for 60 min (repeffusion) in IR group but not in the control group. In both groups,physiologic recorder was used for continuous measurement of bemodynamic parameters including heart rote and mean arterial pressure; full-automated biochemical analyzer was used to determine the serum calcium and cTnT before ischemia and at 60 min after repedusion; quantitative PCR was used to detect the mRNA expression of sarcolemmal calcium transporting channel proteins (NCX 1, LVDCCα-1C and PMCAI ) in cardiomyocytes of the left ventricle (LV, isehemic area) and right ventricle (RV) at 60 min after reperfusion. Results Two groups did not differ in heart rate and mean arterial pressure either before ischemia or at 60 min after reperfusion, but both showed a reduction in these two parameters at 60 min after reperfusion compared with these before ischemia.There was no statistical difference of two groups in serum calcium before ischemia or at 60 min after reperfusion,or at any given time points between two groups. While the plasma cTnT level was comparable before ischemia between two groups. IR group showed significantly elevated cTnT at 60 min after reperfusion compared with the control group[(4.29±2.22) μg/L vs (1.62±0.60) μg/L, P=0.031]. There was statistical difference of two groups in plasma cTnT level before ischemia compared with this at 60 min after reperfusion(all P＜0.05). At 60 min after reperfusion, there were no differences in mRNA expression of sarcolemmal NCXI, LVDCCα-1C and PMCA1 of same ventricle between two groups or between two ventricles of same group (NCX1 : control group LV 50±4,control group RV 47±9; IR group LV 55±6, IR group RV 53±11 ; LVDCCα-1C: control group LV 33±7, control group RV 30±7; IR group LV 28±3, IR group RV 37±5; PMCA1 : control group LV 70±10, control group RV 53± 11 ; IR group LV 66±12, IR group RV 78±8; all P＞0.05). Conclusion The mRNA expression of NCX,LVDCCα-1C and PMCA1 does not change obviously at 20 min after ischemia and at 60 min after reperfusion in rat heart in vivo, suggesting that the quantity of sarcolemmal calcium transporting channel proteins may not be responsible for calcium overload.