title: Effect of sodium-transport inhibitors on airway smooth muscle contractility in vitro.
abstract: 1. To determine whether alterations in membrane sodium transport in airway smooth muscle can alter its contractility, we studied the effect of ouabain (a Na+/K(+)-adenosine triphosphatase inhibitor) and amiloride on contractile responses in bovine trachea and human bronchial rings in a series of studies. 2. Ouabain (10(-6)-10(-4) mol/l) caused concentration-related contraction of bovine trachea with a maximum effect at 30 min; the mean increases in tension with 10(-6), 10(-5) and 10(-4) mol/l ouabain were 19, 27, and 32%, respectively, of the maximum response seen with 10(-3) mol/l histamine (n = 6). In human bronchial rings, ouabain (10(-5) mol/l) caused a mean contraction which was 40% of the maximum response to methacholine (n = 8). 3. Calcium-free fluid (plus ethylenediaminetetraacetic acid) and nifedipine (10(-5) mol/l) inhibited ouabain-induced contractions, suggesting that contraction was mediated in part by calcium entry via voltage-dependent calcium channels. Phentolamine (10(-5) mol/l) was without effect. 4. Ouabain (10(-5) mol/l) did not alter histamine responsiveness in bovine trachea or methacholine responsiveness in human bronchial rings. 5. Amiloride did not affect resting tone in bovine trachea but caused a concentration-dependent relaxation of bovine tracheal strips preconstricted with carbachol, 10(-3) mol/l amiloride relaxing strips completely over 15 minutes (n = 8).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Respiratory Medicine Unit, City Hospital, Nottingham, U.K.
authors.forename: A J
authors.initials: AJ
authors.lastname: Knox
authors.forename: P
authors.initials: P
authors.lastname: Ajao
authors.forename: J R
authors.initials: JR
authors.lastname: Britton
authors.forename: A E
authors.initials: AE
authors.lastname: Tattersfield
mesh_terms: D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D001980:Bronchi / Q000187:drug effects; D002217:Carbachol / Q000494:pharmacology; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D016210:Methacholine Chloride / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000502:physiology*; D009543:Nifedipine / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology*; D010646:Phentolamine / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D014132:Trachea / Q000187:drug effects
chemical_list: D016210:Methacholine Chloride; D010042:Ouabain; D000584:Amiloride; D006632:Histamine; D002217:Carbachol; D000254:Sodium-Potassium-Exchanging ATPase; D009543:Nifedipine; D010646:Phentolamine