title: Propofol attenuates beta-adrenoreceptor-mediated signal transduction via a protein kinase C-dependent pathway in cardiomyocytes.
abstract: BACKGROUND
  Activation of beta adrenoreceptors by catecholamines is an important mechanism for increasing the inotropic state of the heart. The objectives of the current study were to investigate the effects of propofol on beta-adrenoreceptor-mediated increases in cardiomyocyte intracellular Ca2+ concentration ([Ca2+]i), cell shortening, L-type Ca2+ current (ICa) and cyclic adenosine monophosphate (cAMP) accumulation. The authors also investigated the site of action of propofol in the beta-adrenoreceptor signaling pathway, as well as the role of protein kinase C (PKC), and tested the hypothesis that propofol would inhibit the beta-adrenoreceptor signaling pathway via a PKC-dependent mechanism.
  
  
  METHODS
  Freshly isolated ventricular myocytes were obtained from adult rat and guinea pig hearts. Myocyte shortening (video edge detection) and [Ca2+]i (fura-2, 340/380 ratio) were monitored simultaneously in individual cells. Conventional whole cell patch clamp analysis was used to measure the ICa in individual myocytes. cAMP production was assessed in suspensions of myocytes using an enzyme immunoassay kit.
  
  
  RESULTS
  Propofol (0.1-10 mum) had no effect on steady state [Ca2+]i, cell shortening, ICa, or cAMP production. In contrast, propofol caused dose-dependent decreases in isoproterenol-stimulated increases in [Ca2+]i, shortening, ICa, and cAMP. Forskolin-induced increases in [Ca2+]i, shortening, and cAMP production were not altered by propofol. PKC activation with phorbol myristate acetate attenuated isoproterenol-stimulated cAMP production. Inhibition of PKC with bisindolylmaleimide (broad range inhibitor) or Gö 6976 (inhibitor of Ca2+-dependent PKC isoforms) abolished propofol-induced inhibition of isoproterenol-stimulated increases in [Ca2+]i, shortening, and cAMP production.
  
  
  CONCLUSIONS
  Clinically relevant concentrations of propofol attenuate beta-adrenergic signal transduction in cardiac myocytes via inhibition of cAMP production. The inhibitory site of action of propofol is upstream of adenylyl cyclase and involves activation of PKC alpha.
authors.affiliation: Center for Anesthesiology Research, Division of Anesthesiology and Critical Care Medicine, The Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Kurokawa
authors.forename: Paul A
authors.initials: PA
authors.lastname: Murray
authors.forename: Derek S
authors.initials: DS
authors.lastname: Damron
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D000818:Animals; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000378:metabolism; D000242:Cyclic AMP / Q000096:biosynthesis; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects*; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism; D015742:Propofol / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D000318:Adrenergic beta-Agonists; D018686:Anesthetics, Intravenous; D020746:Calcium Channels, L-Type; D004791:Enzyme Inhibitors; D011943:Receptors, Adrenergic, beta; D000242:Cyclic AMP; D011493:Protein Kinase C; D000262:Adenylyl Cyclases; D007545:Isoproterenol; D015742:Propofol