title: Effect of inhibition of extracellular signal-regulated kinase on relaxations to beta-adrenoceptor agonists in porcine isolated blood vessels.
abstract: OBJECTIVE
  Stimulation of vascular beta-adrenoceptors causes vasodilatation through activation of adenylyl cyclase (AC) and plasma membrane potassium channels, and beta-adrenoceptors have been linked to activation of extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase in various cell lines. However, how these findings relate to functional responses in intact tissues is largely unknown. The aim of this study, therefore, was to investigate the role of ERK in beta-adrenoceptor-induced vasodilatation.
  
  
  METHODS
  Segments of porcine coronary artery were mounted in a Mulvany wire myograph and bathed in Krebs-Henseleit buffer gassed with 95% O(2)/5% CO(2) and maintained at 37 degrees C. Tissues were pre-contracted with the thromboxane mimetic U46619, endothelin-1 or KCl. Cumulative concentration-response curves to beta-adrenoceptor agonists or forskolin were then carried out in the absence or presence of the mitogen-activated protein kinase kinase (MEK) inhibitors PD98059 (10 or 50 microM) or U0126 (10 microM).
  
  
  RESULTS
  PD98059 caused a concentration-dependent leftward shift in response to isoprenaline (pEC(50) control, 7.5 +/- 0.1; 50 microM PD98059, 8.1 +/- 0.1: P < 0.05). Inhibition of MEK also enhanced the maximum relaxation seen with salbutamol, but not the responses to the beta(1)-adrenoceptor selective agonist xamoterol or the AC activator forskolin. There was no enhancement of the relaxations to beta-adrenoceptor agonists after inhibition of ERK activation in tissues pre-contracted with KCl or treated with the K(+) channel blocker tetraethylammonium.
  
  
  CONCLUSIONS
  These data indicate that ERK inhibits beta(2)-adrenoceptor-mediated vasodilatation through a mechanism which may involve inactivation of plasma membrane potassium channels.
authors.affiliation: School of Biomedical Sciences, University of Nottingham, Medical School, Nottingham, UK.
authors.forename: C O
authors.initials: CO
authors.lastname: Uhiara
authors.forename: S P H
authors.initials: SP
authors.lastname: Alexander
authors.forename: R E
authors.initials: RE
authors.lastname: Roberts
mesh_terms: D058666:Adrenergic beta-2 Receptor Agonists; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D005419:Flavonoids / Q000008:administration & dosage / Q000494:pharmacology; D009213:Myography; D009570:Nitriles / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013552:Swine; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D058666:Adrenergic beta-2 Receptor Agonists; D000318:Adrenergic beta-Agonists; D002070:Butadienes; D005419:Flavonoids; D009570:Nitriles; D015221:Potassium Channels; C113580:U 0126; D048049:Extracellular Signal-Regulated MAP Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one