Abstract
We investigated the gene expression of β1-adrenergic receptor (β1AR) and stimulatory G-protein Gsα, important signal transduction elements for regulating heart rate and contractility, in ventricle after chronic treatment with isoproterenol (ISO) in rat. Rats were treated with ISO (4 mg/kg, intraperitoneal) twice a day for 4 d. Ventricle weight of the heart and ventricle weight/body weight ratio were increased by 23% and 25% compared with control, respectively. Positive inotropic responses to ISO in left atrial muscle preparations isolated from ISO-treated rats were markedly decreased. Northern blot hybridization showed that the mRNA transcript of β1AR was significantly decreased in ventricle of ISO-treated rats, whereas Gsα mRNA level was unchanged. Present results demonstrate that the gene expression of myocardial β1AR, but not Gsα, was decreased in rat myocardium of ISO-induced cardiac hypertrophy, and suggesting that decrease in the gene expression of β1AR may be one of the mechanisms responsible for the diminished cardiac function.
