title: A role for the sodium pump in H2O2-induced vasorelaxation in porcine isolated coronary arteries.
abstract: Hydrogen peroxide (H2O2) has been proposed to act as a factor for endothelium-derived hyperpolarization (EDH) and EDH may act as a 'back up' system to compensate the loss of the NO pathway. Here, the mechanism of action of H2O2 in porcine isolated coronary arteries (PCAs) was investigated. Distal PCAs were mounted in a wire myograph and pre-contracted with U46619 (1nM-50μM), a thromboxane A2-mimetic or KCl (60mM). Concentration-response curves to H2O2(1μM-1mM), bradykinin (0.01nM-1μM), sodium nitroprusside (SNP) (10nM-10μM), verapamil (1nM-10μM), KCl (0-20mM) or Ca(2+)-reintroduction (1μM-10mM) were constructed in the presence of various inhibitors. Activity of the Na(+)/K(+)-pump was measured through rubidium-uptake using atomic absorption spectrophotometry. H2O2 caused concentration-dependent vasorelaxations with a maximum relaxation (Rmax) of 100±16% (mean±SEM), pEC50=4.18±0.20 (n=4) which were significantly inhibited by PEG-catalase at 0.1-1.0mM H2O2 (P<0.05). 10mM TEA significantly inhibited the relaxation up to 100μM H2O2 (P<0.05). 60mM K(+) and 500nM ouabain significantly inhibited H2O2-induced vasorelaxation producing a relaxation of 40.8±8.5% (n=5) and 47.5±8.6% (n=6) respectively at 1mM H2O2 (P<0.0001). H2O2-induced vasorelaxation was unaffected by the removal of endothelium, inhibition of NO, cyclo-oxygenase, gap junctions, SKCa, IKCa, BKCa Kir, KV, KATP or cGMP. 100μM H2O2 had no effects on the KCl-induced vasorelaxation or Ca(2+)-reintroduction contraction. 1mM H2O2 inhibited both KCl-induced vasorelaxation and rubidium-uptake consistent with inhibition of the Na(+)/K(+)-pump activity. We have shown that the vascular actions of H2O2 are sensitive to ouabain and high concentrations of H2O2 are able to modulate the Na(+)/K(+)-pump. This may contribute towards its vascular actions.
authors.affiliation: Pharmacology Research Group, School of Life Sciences, University of Nottingham Medical School, Queen's Medical Centre, Nottingham NG7 2UH, United Kingdom.
authors.forename: P S
authors.initials: PS
authors.lastname: Wong
authors.affiliation: Pharmacology Research Group, School of Life Sciences, University of Nottingham Medical School, Queen's Medical Centre, Nottingham NG7 2UH, United Kingdom.
authors.forename: M J
authors.initials: MJ
authors.lastname: Garle
authors.affiliation: Pharmacology Research Group, School of Life Sciences, University of Nottingham Medical School, Queen's Medical Centre, Nottingham NG7 2UH, United Kingdom.
authors.forename: S P H
authors.initials: SP
authors.lastname: Alexander
authors.affiliation: Pharmacology Research Group, School of Life Sciences, University of Nottingham Medical School, Queen's Medical Centre, Nottingham NG7 2UH, United Kingdom. Electronic address: michael.randall@nottingham.ac.uk.
authors.forename: M D
authors.initials: MD
authors.lastname: Randall
authors.affiliation: Pharmacology Research Group, School of Life Sciences, University of Nottingham Medical School, Queen's Medical Centre, Nottingham NG7 2UH, United Kingdom.
authors.forename: R E
authors.initials: RE
authors.lastname: Roberts
mesh_terms: D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D002229:Carbenoxolone / Q000494:pharmacology; D002374:Catalase / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D011092:Polyethylene Glycols / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000502:physiology*; D013552:Swine; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology; D014700:Verapamil / Q000494:pharmacology
chemical_list: C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D010069:Oxadiazoles; D010455:Peptides; D011810:Quinoxalines; D014662:Vasoconstrictor Agents; C070295:catalase-polyethylene glycol; D009599:Nitroprusside; D005576:Colforsin; D011092:Polyethylene Glycols; D010042:Ouabain; C064719:iberiotoxin; D006861:Hydrogen Peroxide; D014700:Verapamil; D002374:Catalase; D000254:Sodium-Potassium-Exchanging ATPase; D002229:Carbenoxolone; D001920:Bradykinin; D019331:NG-Nitroarginine Methyl Ester; D007213:Indomethacin
keywords: Bradykinin (PubChem CID: 6026); Ca(2+)-reintroduction; Calcium chloride (PubChem CID: 6093260); Glibenclamide (PubChem CID: 3488); Hydrogen peroxide (H(2)O(2)) relaxation; Hydrogen peroxide (PubChem CID: 784); Indomethacin (PubChem CID: 3715); KCl relaxation; Ouabain (PubChem CID: 439501); Ouabain-sensitive sodium–potassium pump; Porcine coronary artery; Rubidium chloride (PubChem CID: 62683); Rubidium uptake; Tetraethylammonium acetate tetrahydrate (PubChem CID: 2724098); U46619, 9,11-dideoxy-9α,11α-epoxymethanoprostaglandin F(2α) (PubChem CID: 16760624); l-NAME (PubChem CID: 39836)