title: Stimulated release of a hyperpolarizing factor (ADHF) from mesenteric artery perivascular adipose tissue: involvement of myocyte BKCa channels and adiponectin.
abstract: OBJECTIVE
  Perivascular adipose tissue (PVAT) releases adipocyte-derived hyperpolarizing factors (ADHFs) that may partly act by opening myocyte K(+) channels. The present study in rat and mouse mesenteric arteries aimed to identify the myocyte K(+) channel activated by PVAT and to determine whether adiponectin contributed to the hyperpolarizing effects of PVAT.
  
  
  METHODS
  Myocyte membrane potential was recorded from de-endothelialized, non-contracted rat and mouse mesenteric arteries in the presence and absence of PVAT.
  
  
  RESULTS
  The β3 -adrenoceptor agonist, CL-316,243 (10 μM), generated PVAT-dependent, iberiotoxin-sensitive myocyte hyperpolarizations resulting from BKCa channel opening and which were partially blocked by L-NMMA (100 μM). Adiponectin (5 μg·mL(-1) ) also produced iberiotoxin-sensitive hyperpolarizations in PVAT-denuded arterioles. Activation of myocyte AMP-activated protein kinase (AMPK) using 5 μM A-769662 also induced BKCa -mediated hyperpolarizations. Dorsomorphin abolished hyperpolarizations to CL-316,243, adiponectin and A-769662. In vessels from Adipo(-/-) mice, hyperpolarizations to CL-316,243 were absent whereas those to A-769662 and adiponectin were normal. In rat vessels, adipocyte-dependent hyperpolarizations were blocked by glibenclamide and clotrimazole but those to NS1619 (33 μM) were unaltered.
  
  
  CONCLUSIONS
  Under basal, non-contracted conditions, β3 -adrenoceptor stimulation of PVAT releases an ADHF, which is probably adiponectin. This activates AMPK to open myocyte BKCa channels indirectly and additionally liberates NO, which also contributes to the observed PVAT-dependent myocyte hyperpolarizations. Clotrimazole and glibenclamide each reversed hyperpolarizations to adiponectin and A-769662, suggesting the involvement of myocyte TRPM4 channels in the ADHF-induced myocyte electrical changes mediated via the opening of BKCa channels.
authors.affiliation: The University of Manchester, Manchester, UK.
authors.forename: A H
authors.initials: AH
authors.lastname: Weston
authors.forename: I
authors.initials: I
authors.lastname: Egner
authors.forename: Y
authors.initials: Y
authors.lastname: Dong
authors.forename: E L
authors.initials: EL
authors.lastname: Porter
authors.forename: A M
authors.initials: AM
authors.lastname: Heagerty
authors.forename: G
authors.initials: G
authors.lastname: Edwards
mesh_terms: D052242:Adiponectin / Q000378:metabolism*; D058667:Adrenergic beta-3 Receptor Agonists / Q000494:pharmacology*; D000818:Animals; D001713:Biphenyl Compounds; D004149:Dioxoles / Q000494:pharmacology; D005786:Gene Expression Regulation; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials; D008638:Mesenteric Arteries / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D032342:Muscle Cells / Q000502:physiology*; D011753:Pyrones / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D022702:Receptors, Adrenergic, beta-3 / Q000378:metabolism; D050053:TRPM Cation Channels / Q000378:metabolism*; D013876:Thiophenes / Q000494:pharmacology*
chemical_list: D052242:Adiponectin; D058667:Adrenergic beta-3 Receptor Agonists; D001713:Biphenyl Compounds; D004149:Dioxoles; D051036:Large-Conductance Calcium-Activated Potassium Channels; D011753:Pyrones; D022702:Receptors, Adrenergic, beta-3; D050053:TRPM Cation Channels; D013876:Thiophenes; C076126:disodium (R,R)-5-(2-((2-(3-chlorophenyl)-2-hydroxyethyl)-amino)propyl)-1,3-benzodioxole-2,3-dicarboxylate; C512408:4-hydroxy-3-(4-(2-hydroxyphenyl)phenyl)-6-oxo-7H-thieno(2,3-b)pyridine-5-carbonitrile
keywords: 243; AMP kinase; BKCa channels; CL-316; adipocyte-derived hyperpolarizing factor; adiponectin; adipose tissue; iberiotoxin; membrane potential; vascular myocytes; β3-adrenoceptors