Abstract: Objective To study the reasons and mechanism of cardiomyocyte apoptosis in chronic heart failure by using Losartan and to provide a theoretical basis for the treatment of chronic heart failure. Methods The models of chronic heart failure were produced by injecting Adriamycin and Losartan as intervention agents, the expression of apoptotic protein Bax, Bcl-2 and channel protein ERK1, JNK1 and P38MAPK were detected by immunohistochemistry and RT-PCR．Cardiomyocyte apoptosis and myocardial ultrastructure are detected by transmission electron microscopy and TUNEL staining. Results Compared with the model group of heart failure, after Losartan treatment, the ultra structure of myocardial cells were significantly improved, Apoptosis index was decreased significantly (EM>P /EM><0.01), The level of Bax and JNK1 decreased (Bax χSUP>2/SUP> =6.6149, EM>P/EM> =0.0078; JNK1 EM>q/EM> =22.156，EM>P /EM><0.01）. However, the expressions of ERK1 and Bcl-2 were significantly increased (ERK1 EM>q /EM>=15.3514，EM>P /EM><0.01；Bcl-2 χSUP>2/SUP> =6.81,EM>P

Key words: Losartan, Chronic heart failure, Extracellular signal-regulated kinase, Jun N-terminal kinase, Mitogen-activated protein kinase, Immunohistochemistry, RT-PCR, Rat