Effect of Metoprolol on β_3-adrenoceptor mRNA Expression in Rats with Chronic Heart Failure

Objective]To investigate the changes of β3-adrenoceptor (β3AR) mRNA expression in the rats with heart failure, and to explore the effect of metoprolol on β3 mRNA expression. [Methods] Twenty-eight rats were randomly divided into sham operated group (n=10) and heart failure group (n=18). Rat model was established by aortic constriction. The rats in heart failure group were divided into heart failure control group and metoprolol group three months after operation (eight rats in each group). Metoprolol was started orally with 6 mg·kg-1·d-1, isometric saline was started in heart failure control group. After three months of drug therapy, measurement of hemodynamics, index of ventricular weight, the level of βAR mRNA expression were performed. [Results] Compared with sham operated group, left ventricular end systolic pressure (LVESP), and the absolute values of maximal rate of rise and fall (±dp/dt) of left ventricular pressure were all significantly decreased (P 0.01), left ventricular end diastolic pressure (LVEDP) was significantly increased in heart failure control group (P 0.01). In comparison with heart failure control group, the hemodynamic index was significant improved in metoprolol group (P 0.01). The index of ventricular mass was higher in heart failure control group than metoprolol group and Sham group (P 0.01). Compared with Sham group, the level of β3AR mRNA expression was significantly increased in heart failure control group and metoprolol group (P 0.01), but there was no significant difference between the two groups (P 0.05). [Conclusion]The level of β3AR mRNA expression remarkably increased in the rats' ventricles with heart failure. Metoprolol can effectively attenuate left ventricular remodeling and improve hemodynamics, but has no effect on β3AR mRNA expression.