Objective    To investigate the cardiomyocyte apoptosis and protein expressions of bcl-2 and bax in adriamycin (ADM)-induced myocardial damage in rats treated with neuregulin-1β (NRG-1β).     Methods    Sixty male SD rats weighing 200 to 250 g were randomly divided into 3 groups: control

ADR-DCM and ADR+NRG groups. ADR-DCM group (n=20) was weekly injected 2.0 mg/kg of ADR via tail vein once a week for 8 weeks to produce cardiomyopathy. The rats of ADR+NRG group (n=20) was given an injection of NRG-1β at 10 μg/(kg·d) via tail vein for 5 d after the establishment of cardiomyopathy by ADR injection. The animals from control group (n=20) received 2 ml/kg normal saline by injection

once a week for 8 weeks. Nine weeks later

rats were executed under anesthesia and their heart was resected. Apoptotic cardiomyocytes were detected by using the terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) method. The expressions of bcl-2 and bax protein were determined by Western blotting.     Results    The index of apoptotic cardiomyocytes was increased significantly in ADR-DCM group and ADR+NRG group compared with control group (P0.05)

and compared with ADR-DCM group

the index of apoptotic cardiomyocytes was significantly lower in ADR+NRG group (P0.05); compared with ADR-DCM group

the expressions of bcl-2 protein was increased significantly (P0.05)

and the expression of bax protein was induced significantly decreased in ADR+NRG group (P0.05).     Conclusion    NRG-1β suppresses cardiomyocyte apoptosis induced by ADR by upregulating the expression of bcl-2 and downregulating the expression of bax.