Effects of Tetrodotoxin Cardioplegia on Cardiomyocyte Apoptosis and Related Protein Expression in Rat Hearts

OBJECTIVE To explore the effects of tetrodotoxin(TTX) cardioplegia on cardiomyocyte apoptosis and related protein expressions in rat hearts. METHODS Twenty four wistar rats were randomly divided into 3 groups(n=8): Base 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 expressions of Bcl-2 ,Bax protein were detected by immunohistochemical assay in cardiomyocyte. Additionlly 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 Base 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 Base group（2.52±0.58）％ (P<0.01)by immunohistochemical assay.Bax PEI in STH-2 group(8.04±0.57)％increased as compared with TTX group(6.05±0.46)％and Base group（2.14±0.57）％ (P<0.01)by immunohistochemical assay.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 Base group（23.7±2.61）％ (P<0.01)by Western blot. There was no sign of p53 protein expression in all groups by immunohistochemical assay in our experiment．CONCLUSION Compared with STH-2,TTX cardioplegia were all eviating the apoptosis of rat cardiomyocytes.The mechanism was probably up-regulating expression of Bcl-2 protein,down-regulating expression of bax protein and increasing Bcl-2/Bax.