Cardiomyocyte apoptosis and related gene expression after acute myocardial infarction in rats

AIM: To investigate cardiomyocyte apoptosis and the expression of caspase-3,Bcl-2 and Bax after acute myocardial infarction(AMI) in rats.METHODS: AMI model was established with the ligation of left coronary artery in 78 randomly selected female SD rats.Twenty-four hours after operation,43 survivors were randomly divided into 48-hour and 4-week two groups according to the time points: MI 48 h(n=11) and MI4 weeks(n=13) groups,shamoperated rats(S,n=27) were also randomly selected and reassigned to S48 h (n=10) and S4 weeks(n=10) groups.Cardiomyocyte apoptosis was detected with in situ terminal deoxynucleotidyl transferase(TdT)-dUTP nick-end labeling(TUNEL staining) and DNA gel electrophoresis.Caspase-3,Bcl-2 expression and Bax expression were detected with immunohistochemistry and Western blotting analysis.RESULTS: Compared with sham-operated group,after AMI,systolic, diastolic,and mean arterial blood pressures(SBP,DBP,MAP),left ventricular systolic pressure(LVSP) and the maximum change rate of left ventricular pressure rise and fall(±dp/dt) were significantly decreased(P0.05,P0.01),while left ventricular end diastolic pressure(LVEDP) was significantly increased(P0.05) in MI 48 h group.All the above indices in MI 4 weeks group had the same change as that in MI48h group,with the LVEDP significantly higher(P0.01),except for a non-significantly change in SBP,DBP and MAP(all P0.05).In both MI 48 h and MI 4 weeks groups,myocyte apoptotic index was significantly increased in the infracted/scar,border and non-infarcted areas(P0.05,P0.01) with caspase-3 and Bax expressions increased significantly(P0.05,P0.01) in myocytes of the above three areas and Bcl-2 expression increased only in myocytes of the infracted area in MI 48 h group.Western blotting indicated that Bcl-2/Bax ratio was also decreased in MI 48 h subgroup.CONCLUSIONS: After AMI in rats,cardiomyocyte apoptosis happened in the infarction/scar,border and non-infarcted areas,with caspase-3 and Bax expression in myocytes increased,and with Bcl-2 expression increased in myocytes of infracted area and Bcl-2/Bax ratio decreased only early after AMI.