Objective:To explore the effect of two kinds of cardioplegia on cardiomyocyte apoptosis and the related protein expressions in rat hearts. Methods:24 Wistar rats were randomly divided into 3 groups(n=8):Control group

STH-2 group and TTX group. Isolated rat Langendorff and Neely working heart models were estabished. The changes in cardiomyocyte apoptosis were detected by TUNEL.The expression of Bcl-2 and Bax protein were detected by immunohistochemical assay in cardiomyocyte. The expression of Bcl-2 protein in cardiomyocyte was detected by Western blot. Results:Apoptosis index(AI) in STH-2 group(11.20±0.79)% was significantly higher than that in TTX group(6.92±1.10)% and Control group(1.34±0.23)%(P<0.01).Bcl-2 protein expression index(PEI) in TTX group(22.63±1.10)% increased as compared with STH-2 group (13.51±0.67)% and Control group(2.52±0.58)%(P<0.01). Bax PEI in STH-2 group(8.04±0.57)%increased as compared with TTX group(6.05±0.46)% and Control group(2.14±0.57)%(P<0.01). Bcl-2/Bax was 3.78±0.41 in TTX group

1.75±0.15 in STH-2 group. Bcl-2 protein expression in TTX group(86.1±0.98)% increased as compared with STH-2 group(53.2±1.76)% and Control group(23.7±2.61)%(P<0.01). There was no sign of p53 protein expression in all groups. Conclusion:Compared with STH-2

TTX cardioplegia alleviates the apoptosis of rat cardiomyocytes. The mechanism is probably up-regulating expression of Bcl-2 protein

down-regulating expression of bax protein and increasing Bcl-2/Bax.