Effects Of Tetrodotoxin Cardioplegia On Cardiomyocyte Apoptosis And Related Protein Expressions In Rat Hearts

Objective: To explore the effects of tetrodotoxin(TTX) cardioplegia on cardiomyocyte apoptosis and related protein expressions in rat hearts .Methods: 24 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 heart models in Base group were continuously perfused with K-H buffer solution for 60 minutes as a control group. After beating 60 minuters,the hearts in STH-2 group and TTX group were arrested by St.ThomasⅡand TTX cardioplegia for 60 minutes, and then reperfused with K-H buffer solution for 60 minutes. The changes in cardiomyocyte apoptosis were detected by TUNEL, the expressions of Bcl-2 ,Bax and p53 protein were detected by immunohistochemical assay in cardiomyocyte. Additionlly the expression of Bcl-2 protein in cardiomyocyte was detected by Western blot.Results: More apoptotic cardiomytocytes were found in both TTX and STH-2 group than that in Base group . Apoptosis index(AI) in TTX group (6.92±1.10%) and STH-2 group (11.20±0.79%) was significantly higher than that in Base group(1.34±0.23%,P <0.01),while AI in TTX group was lower than that in STH-2 group(P <0.01).Bcl-2 protein expression index(PEI) in both TTX and STH-2 group increased as compared with Base group(2.52±0.58%,P <0.01)by immunohistochemical assay , while Bcl-2 protein in TTX group was higher expression than that in STH-2 group (22.63±1.10%vs 13.51±0.67% , P < 0.01). Bax PEI in both TTX group and STH-2 group increased as compared with Base group(2.14±0.57%,P < 0.01)by immunohistochemical assay, but Bax protein in TTX group was lower expression than that in STH-2 group (6.05±0.46% vs 8.04±0.57%, P < 0.01). Bcl-2/Bax was (3.78±0.41) in TTX group,(1.75±0.15)in STH-2 group,( 1.19±0.08)in Base group . The protein expression of p53 in different group was not detected.Bcl-2 protein expression in both TTX and STH-2 group increased as compared with Base group(23.7±2.61%,P <0.01)by Western blot, while Bcl-2 protein expression in TTX group was higher than that in STH-2 group (86.1±0.98% vs 53.2±1.76%, P < 0.01).Conclusion: Compared with traditional STH-2 cardioplegia ,TTX cardioplegia had better myocardial protective effects on MIRI by alleviating the apoptosis of rat cardiomyocytes. The mechanism was probably up-regulating expression of anti-apoptosis Bcl-2 protein , down-regulating expression of pro-apoptosis bax protein and increasing Bcl-2/Bax.