title: Alpha(1)-AR-induced positive inotropic response in heart is dependent on myosin light chain phosphorylation.
abstract: The possible involvement of different kinases in the alpha(1)-adrenoreceptor (AR)-mediated positive inotropic effect (PIE) was investigated in rat papillary muscle and compared with beta-AR-, endothelin receptor- and phorbol ester-induced changes in contractility. The alpha(1)-AR-induced PIE was not reduced by the inhibitors of protein kinase C (PKC), MAPK (ERK and p38), phosphatidyl inositol 3-kinase, or calmodulin kinase II. However, PKC inhibition attenuated the effect of phorbol 12-myristate 13-acetate (PMA) on contractility. alpha(1)-AR-induced PIE was reduced by approximately 90% during inhibition of myosin light chain kinase (MLCK) by 1-(5-chloronaphthalene-1-sulfonyl)1H-hexahydro-1,4-diazepine (ML-9). Endothelin-induced PIE was also reduced by ML-9, but ML-9 had no effect on beta-AR-induced PIE. The Rho kinase inhibitor Y-27632 also reduced the alpha(1)-AR-induced PIE. The alpha(1)-AR-induced PIE in muscle strips from explanted failing human hearts was also sensitive to MLCK inhibition. alpha(1)-AR induced a modest increase in (32)P incorporation into myosin light chain in isolated rat cardiomyocytes. This effect was eliminated by ML-9. The PIE of alpha(1)-AR stimulation seems to be dependent on MLCK phosphorylation.
authors.affiliation: Department of Pharmacology, University of Oslo, Norway. g.o.andersen@labmed.uio.no
authors.forename: Geir Øystein
authors.initials: GØ
authors.lastname: Andersen
authors.forename: Eirik
authors.initials: E
authors.lastname: Qvigstad
authors.forename: Iwona
authors.initials: I
authors.lastname: Schiander
authors.forename: Halfdan
authors.initials: H
authors.lastname: Aass
authors.forename: Jan-Bjørn
authors.initials: JB
authors.lastname: Osnes
authors.forename: Tor
authors.initials: T
authors.lastname: Skomedal
mesh_terms: D000818:Animals; D001381:Azepines / Q000494:pharmacology; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D002273:Carcinogens / Q000494:pharmacology; D002316:Cardiotonic Agents / Q000494:pharmacology*; D019332:Endothelin-1 / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D007545:Isoproterenol / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology; D018994:Myosin Light Chains / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010210:Papillary Muscles / Q000187:drug effects / Q000201:enzymology*; D010656:Phenylephrine / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism*; D017466:Receptors, Endothelin / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D054460:rho-Associated Kinases
chemical_list: D001381:Azepines; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002273:Carcinogens; D002316:Cardiotonic Agents; D019332:Endothelin-1; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D007545:Isoproterenol; D018994:Myosin Light Chains; D010656:Phenylephrine; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D017346:Protein Serine-Threonine Kinases; D018340:Receptors, Adrenergic, alpha-1; D017466:Receptors, Endothelin; D013755:Tetradecanoylphorbol Acetate; D054460:rho-Associated Kinases; C056218:ML 9