title: Role of nitric oxide in the development and partial reversal of allergen-induced airway hyperreactivity in conscious, unrestrained guinea-pigs.
abstract: 1. Using a conscious, unrestrained guinea-pig model of allergic asthma, we investigated the role of endogenous nitric oxide (NO) in the regulation of airway (hyper)reactivity to histamine before and after the allergen-induced early and late asthmatic reactions, by examining the effect of inhalation of the NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 12 mM, 15 min) on the histamine-induced airway obstruction of ovalbumin-sensitized guinea-pigs before, and at 5.5 h and 23.5 h after allergen challenge. 2. Before allergen challenge, inhaled L-NAME caused a significant 2.02+/-0.25 fold increase (P<0.01) in airway reactivity to histamine; this effect was reversed within 2.5 to 6 h after administration. 3. After the allergen-induced early asthmatic reaction at 5 h after ovalbumin provocation, a significant 3.73+/-0.67 fold increase (P<0.01) of the airway reactivity to histamine was observed; subsequent inhalation of L-NAME at 5.5 h had no effect on the airway hyperreactivity, reassessed at 6 h. 4. After the late asthmatic reaction, at 23 h after ovalbumin provocation, a reduced, but still significant airway hyperreactivity to histamine (2.18+/-0.40 fold; P<0.05) was observed. Subsequent inhalation of L-NAME now significantly potentiated the partially reduced airway hyperreactivity 1.57+/-0.19 fold (P<0.05) to the level observed after the early asthmatic reaction. 5. When administered 30 min before allergen exposure, L-NAME significantly enhanced the allergen-induced early asthmatic reaction. However, when administered at 5.5 h after allergen provocation, L-NAME did not affect the subsequent late asthmatic reaction. 6. These results indicate that endogenous NO is involved the regulation of histamine- and allergen-induced bronchoconstriction and that a deficiency of cNOS-derived NO contributes to the allergen-induced airway hyperreactivity to histamine after the early asthmatic reaction, while a recovery of NO deficiency may account for the partial reversal of the allergen-induced airway hyperreactivity after the late asthmatic reaction.
authors.affiliation: Department of Molecular Pharmacology, University Centre for Pharmacy, Groningen, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Schuiling
authors.forename: A B
authors.initials: AB
authors.lastname: Zuidhof
authors.forename: M A
authors.initials: MA
authors.lastname: Bonouvrie
authors.forename: N
authors.initials: N
authors.lastname: Venema
authors.forename: J
authors.initials: J
authors.lastname: Zaagsma
authors.forename: H
authors.initials: H
authors.lastname: Meurs
mesh_terms: D000485:Allergens / Q000494:pharmacology*; D000818:Animals; D016535:Bronchial Hyperreactivity / Q000139:chemically induced / Q000503:physiopathology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*
chemical_list: D000485:Allergens; D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D006632:Histamine; D019331:NG-Nitroarginine Methyl Ester