Background:Calcium regulatory proteins-L-type Ca2+ channels (LTCCs),ryanodine receptor 2 (RyR2),and Na+/Ca2-exchanger isoform 1 (NCX1) have been recognized as important protective mechanisms during myocardial ischemia-reperfusion injury (I/RI).Both sevofturane postconditioning (SevoPoC) and delayed remote ischemic preconditioning (DRIPC) have been shown to protect the heart against I/RI.In this study,we aimed to compare the effects of SevoPoC and DRIPC on the expression of the three calcium regulatory proteins in an isolated rat heart model.Methods:After 30-min balanced perfusion,isolated hearts from rats were subjected to 30-min ischemia followed by 60-min reperfusion.Totally 40 isolated hearts were randomly assigned to four groups (n =10/group):time control group,I/RI group,SevoPoC group,and DRIPC group.The effect of SevoPoC (3％ v/v) and DRIPC were observed.Myocardial infarct size (IS),cardiac troponin I level,and heart function were measured.The protein and messenger RNA levels of LTCCs,RyR2,and NCX1 were determined.Results:Both SevoPoC and DRIPC improved the recovery of myocardial function,and reduced cardiac troponin Ⅰ release after I/RI.The decrease in IS was more significant in the SevoPoC group than that in the DRIPC group (16.50％ ± 4.54％ in the SevoPoC group [P =0.0006],and 22.34％ ± 4.02％ in the DRIPC group [P =0.0007] vs.35.00％ ± 5.24％ in the I/RI group,respectively).SevoPoC,but not DRIPC significantly inhibited the activity of NCX 1 (0.59 + 0.09 in the I/RI group vs.0.32 ± 0.16 in the SevoPoC group,P =0.006;vs.0.57 ± 0.14 in the DRIPC group,P =0.072).No statistical significant differences were observed in the expression of LTCCs and RyR2 between SevoPoC and DRIPC.In addition,subsequent correlation analysis showed a significantly positive relationship between the cardiac troponin Ⅰ level and the protein expression ofNCX1 (r =0.505,P =0.023).Conclusion:SevoPoC may be more effective in the cardioprotection than DRIPC partly due to the deactivation ofNCX1.