Study Of Expression Of CTnT Fetal Isoforms And Cardiac Apoptosis In Failing Myocardium

Objectives: To investigate whether the degree of heart failure affects the expression of cardiac tropomn T (cTnT) isoforms of Chinese people. To investigate whether myocyte apoptosis is involved in ventricular remodeling in cardiac hypertrophy and heart failure. To investigate whether cardiac apoptosis participates in the transition from left ventricular hypertrophy (LVII) to left ventricular dysfunction (LVD). Methods: The left ventricular and right atrial myocardium were obtained from normal dornal hearts or heart failure patients undegoing cardiac operation. Using western-blot to detect the differences in the expression of cTnT fetal isoforms between normal and failing human myocardium. Cardiac myocyte apoptotic events were studied in a rat model of LVII and LVI) induced by transverse aortic constriction above the kidney arteries, excision of left kidney and drinking 1% brine. Using TdT-mediated dUTP nick end-labeling (TUN7EL) to detect cardiac myocyte apoptosis in the rat model. Results : The expression of cTnT4 increased from undetectable in normal adult hearts to 4.5?.3 in NYI-IA grade 2 ,18.7?.5 in NYHA grade 3 and 4. The expression of cTnT2 was found in a right atrial myocardium from a adult patient with severe heart failure. A similar distribution between LVII and LVI) was found 16 weeks after surgery, so 16 weeks after operation is the time point when LVII transited to LVI) in our rat model. None of controls showed any evidence of apoptosis. There was more cardiac apoptosis in left ventricles in LVII rats 16 weeks after operation than in LVII rats 7 weeks after operation. But there was no difference in cardiac apoptosis in right ventricles between the two groups. Cardiac apoptosis majorly exsisted in the subendocardial and midwall regions of LVII rats. When LVII transited to LVD, the number of apoptosis increased markedly in left and right ventricles. At 16 weeks after operation, we examined cardiac apoptosis between the rats that had suffered heart failure 2 weeks before and the rats that had suffered heart failure no more than 2 weeks,and found no difference.Fibrosis also increased in LVII and LVI) rats.there was a higher incidence of apoptotic events of cardiomyocyte origion in regions bordering fibrosis than other regions. Conclusion: Expression of cTnT4 increased with the deterioration of cardiac function in Chinese people. Myocyte death through apoptosis occurs during myocardial remodeling in hypertrophy and heart failure in response to chronic pressure ?? overload. Cardiomyocyte-spccific apoptosis also contributes to the transition from LVH to LVD.