title: [Effects of beta3-adrenergic receptors agonist on beating rate and cAMP levels in cultured cardiomyocytes of rats].
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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).
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of cardiology, The First Clinical College of Harbin Medical University, Harbin 150001, China.
authors.forename: Yi-hui
authors.initials: YH
authors.lastname: Kong
authors.forename: Wei-min
authors.initials: WM
authors.lastname: Li
authors.forename: Ying
authors.initials: Y
authors.lastname: Tian
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D004983:Ethanolamines / Q000494:pharmacology*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D022702:Receptors, Adrenergic, beta-3 / Q000378:metabolism
chemical_list: D000318:Adrenergic beta-Agonists; D004983:Ethanolamines; D012333:RNA, Messenger; D022702:Receptors, Adrenergic, beta-3; C057368:BRL 37344; D000242:Cyclic AMP