Effects of endogenous superoxide anion and nitric oxide on cholinergic constriction of normal and hyperreactive guinea pig airways.
In a guinea pig model of allergic asthma, we have recently established that a deficiency of nitric oxide (NO) contributes to the increased ex vivo responsiveness of isolated perfused tracheae to methacholine after the early asthmatic reaction at 6 h after inhalational challenge of the animals with ovalbumin aerosol. Because this deficiency could be caused by a reaction of NO with enhanced levels of inflammation-induced superoxide anion (O-2), we examined the effect of endogenous O-2 on the regulation of methacholine-induced constriction by NO of intact perfused tracheal tube preparations from unchallenged (control) guinea pigs and from animals 6 h after ovalbumin challenge. In the presence of the NO synthase (NOS) inhibitor N omega-nitro-L-arginine methyl ester (L-NAME; 100 microM), tracheae obtained from unchallenged guinea pigs showed a 1.7-fold increase in the maximal response to intraluminally applied methacholine (p < 0.05). By contrast, the maximal airway response to methacholine was significantly decreased in the presence of the O-2 scavenger superoxide dismutase (SOD; 100 U/ml), by approximately 45% (p < 0.01). The SOD-induced decrease in responsiveness to methacholine was reversed by L-NAME. Tracheal preparations obtained at 6 h after allergen challenge showed a 1. 8-fold increased responsiveness to intraluminally applied methacholine compared with controls (p < 0.001), which was not further enhanced in the presence of L-NAME. SOD had neither an effect on the increased responsiveness nor did it restore the potentiating effect of L-NAME. These results indicate that (1) in normoreactive tracheal preparations, the regulatory role of NO is partially counteracted by endogenous O-2, and ( 2) the deficiency of NO in hyperreactive tracheae obtained at 6 h after ovalbumin challenge is not caused by its reaction with O-2, but rather to decreased cNOS activity. De Boer J, Pouw FMH, Zaagsma J, Meurs H. Effects of endogenous superoxide anion and nitric oxide on cholinergic constriction of normal and hyperreactive guinea pig airways.
De Boer
J
J
Department of Molecular Pharmacology, University Centre for Pharmacy, Groningen, The Netherlands.
Pouw
F M
FM
Zaagsma
J
J
Meurs
H
H
D000280:Administration, Inhalation; D000336:Aerosols; D000485:Allergens / Q000008:administration & dosage / Q000276:immunology; D000818:Animals; D001249:Asthma / Q000503:physiopathology; D001980:Bronchi / Q000187:drug effects*; D016535:Bronchial Hyperreactivity / Q000503:physiopathology*; D016085:Bronchoconstrictor Agents / Q000494:pharmacology*; D001993:Bronchodilator Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002799:Cholinergic Fibers / Q000187:drug effects*; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D006168:Guinea Pigs; D007114:Immunization; D016210:Methacholine Chloride / Q000494:pharmacology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010047:Ovalbumin / Q000008:administration & dosage / Q000276:immunology; D010277:Parasympathomimetics / Q000494:pharmacology*; D013482:Superoxide Dismutase / Q000494:pharmacology; D013481:Superoxides / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D014132:Trachea / Q000187:drug effects
D000336:Aerosols; D000485:Allergens; D016085:Bronchoconstrictor Agents; D001993:Bronchodilator Agents; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D010277:Parasympathomimetics; D016210:Methacholine Chloride; D013481:Superoxides; D009569:Nitric Oxide; D010047:Ovalbumin; D019001:Nitric Oxide Synthase; D013482:Superoxide Dismutase; D019331:NG-Nitroarginine Methyl Ester