Effects of beta3-adrenergic receptors agonist on beating rate and cAMP levels in cultured cardiomyocytes of rats / 中国应用生理学杂志

ABSTRACT

<p><b>AIM</b>To evaluate the effects of beta3-adrenergic receptors (ARs) agonist (BRL-37344) on beating rate and cAMP levels and investigate the influence on the chronotropic action of beta3-ARs in cultured cardiomyocyte of rats.</p><p><b>METHODS</b>Cultured neonatal rat cardiomyocytes were divided randomly into eight groups, control group, ISO group, Nadolol + ISO group, BRL group, PIX + BRL group, L-NAME + BRL group, Nadolol + BRL group and Bupranolol + BRL group. Beating rate of culture neonatal rat cardiomyocytes was observed and cAMP measured by enzyme immunoassay kit. Expression levels of beta3-ARs mRNA in cardiomyocytes was evaluated by reverse transcription-polymerase chain reaction (RT-PCR).</p><p><b>RESULTS</b>ISO, nonspecific beta-ARs agonist increased beating rate and intracellular cAMP production, antagonized by Nadolol, beta1, beta2-ARs antagonist. BRL37344 decreased beating rate and intracellular cAMP levels. FPTX, Gi protein inhibitor and Bupranolol, nonspecific beta-ARs antagonist totally blocked the effect and L-NAME, nitric oxide synthase (NOS) inhibitor partly blocked the effect, but Nadolol did not. There was the expression of beta3-AR mRNA in cardiomyocytes by RT-PCR.</p><p><b>CONCLUSIONS</b>Beta3-ARs showed in cardiomyocytes and produced negative chronotropic effects. beta1, beta2-ARs antagonist did not affect it. It suggested beta3-ARs signal transduction was related with G1 protein. The negative inotropic effect of beta3-ARs stimulation was mediated by activation of the NOS pathway.</p>