title: Roles of PKA, PI3K, and cPLA2 in the NO-mediated negative inotropic effect of beta2-adrenoceptor agonists in guinea pig right papillary muscles.
abstract: Although beta(2)-adrenoceptors represent 15-25% of beta-adrenoceptors in the guinea pig heart, their functionality is controversial. We assessed the inotropic effects of beta(2)-adrenoceptor partial agonists in right papillary muscles. Salbutamol induced a small but significant concentration-dependent negative inotropic effect (NIE, -5% at 60 nM) followed by a moderate positive inotropic effect (+36% at 6 microM) due to activation of beta(1)-adrenoceptors. In the presence of 4 microM atenolol, the concentration-dependent NIE (-12% at 6 microM) was biphasic, best described by a double logistic equation with respective EC(50) values of 3 and approximately 420 nM, and was insensitive to SR59230A. In muscles from pertussis toxin-treated guinea pigs, the salbutamol-induced positive inotropic effect was sensitive to low concentrations of ICI-118551 in an unusual manner. Experiments in reserpinized animals revealed the importance of the phosphorylation-dephosphorylation processes. PKA inhibition reduced and suppressed the effects obtained at low and high concentrations, respectively, indicating that its activation was a prerequisite to the NIE. The effect occurring at nanomolar concentrations depended upon PKA/phosphatidylinositol 3-kinase/cytosolic phospholipase A(2) (cPLA(2)) activations leading to nitric oxide (NO) release via the arachidonic acid/cyclooxygenase pathway. NO release via PKA-dependent phosphorylation of the receptor was responsible for the inotropic effect observed at submicromolar concentrations, which is negatively controlled by cPLA(2). The possibility that these effects are due to an equilibrium between different affinity states of the receptor (G(s)/G(i) coupled and G(i) independent with different signaling pathways) that can be displaced by ICI-118551 is discussed. We conclude that beta(2)-adrenoceptors are functional in guinea pig heart and can modulate the inotropic state.
authors.affiliation: Centre National de Recherche Scientifique UMR 6542, Physiologie des Cellules Cardiaques et Vasculaires, Faculté des Sciences, Université François-Rabelais, Tours, France.
authors.forename: Fabien A
authors.initials: FA
authors.lastname: Faucher
authors.forename: François E
authors.initials: FE
authors.lastname: Gannier
authors.forename: Jacques M
authors.initials: JM
authors.lastname: Lignon
authors.forename: Pierre
authors.initials: P
authors.lastname: Cosnay
authors.forename: Claire O
authors.initials: CO
authors.lastname: Malécot
mesh_terms: D058665:Adrenergic beta-1 Receptor Agonists; D058666:Adrenergic beta-2 Receptor Agonists; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000420:Albuterol / Q000494:pharmacology*; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D001262:Atenolol / Q000494:pharmacology; D002395:Catecholamines / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D003864:Depression, Chemical; D004305:Dose-Response Relationship, Drug; D054333:Drug Partial Agonism; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D054513:Group IV Phospholipases A2 / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009569:Nitric Oxide / Q000378:metabolism*; D010210:Papillary Muscles / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010766:Phosphorylation; D011412:Propanolamines / Q000494:pharmacology; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D018342:Receptors, Adrenergic, beta-1 / Q000378:metabolism; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
chemical_list: C097869:3-(2-ethylphenoxy)-1-(1,2,3,4-tetrahydronaphth-1-ylamino)-2-propanol oxalate; D058665:Adrenergic beta-1 Receptor Agonists; D058666:Adrenergic beta-2 Receptor Agonists; D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D002395:Catecholamines; D011412:Propanolamines; D018342:Receptors, Adrenergic, beta-1; D018343:Receptors, Adrenergic, beta-2; D016718:Arachidonic Acid; D009569:Nitric Oxide; C026777:ICI 118551; D001262:Atenolol; D011451:Prostaglandin-Endoperoxide Synthases; D019869:Phosphatidylinositol 3-Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D054513:Group IV Phospholipases A2; D010744:Phosphoric Monoester Hydrolases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D000420:Albuterol