title: Effect of dexamethasone on airway inflammation and responsiveness after antigen challenge of the rat.
abstract: The purpose of this study was to examine the effects of dexamethasone on airway responsiveness and lung inflammation of rats at 8 h, 32 h, and 7 d after allergen challenge. Brown-Norway male rats, 7 to 8 wk old, were actively sensitized to ovalbumin (OA) and challenged 14 d later. The rats were divided into a control group (n = 31) and a test group (n = 34) that received dexamethasone (DEXA) (0.3 mg/kg intraperitoneally) 14 h and 2 h before saline or OA challenge. For challenge, rats were anesthetized with pentobarbital and intubated endotracheally. Aerosols of OA (5% wt/vol in saline) were administered for 5 min. Responsiveness to inhaled aerosols of methacholine and the total and differential leukocyte counts in the large airways (generations 0 to 5), small airways, and parenchyma isolated by tissue mincing and digestion were measured at 8 h, 32 h, and 7 d after OA challenge. The cellular influx into the airways and parenchyma was highest at 8 h and decreased progressively over 7 d. DEXA significantly inhibited the cellular influx after allergen challenge. At 8 h, cellular return from the large airways was 3.61 +/- 0.5 x 10(6) (controls) versus 1.0 +/- 0.2 x 10(6) (DEXA), and from the small airways and parenchyma was 31.7 +/- 2.8 x 10(6) (controls) versus 21.9 +/- 2.9 x 10(6) (DEXA) (p < 0.05). The differences were attributable mostly to decreases in neutrophils in DEXA-treated animals. In control animals, neutrophil yield fell between 8 and 32 h, whereas eosinophils and 32 h, whereas eosinophil and lymphocyte counts increased.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Respiratory Health Network of Centres of Excellence, André Viallet Research Institute, St-Luc Hospital, University of Montreal, Quebec, Canada.
authors.forename: P M
authors.initials: PM
authors.lastname: Renzi
authors.forename: R
authors.initials: R
authors.lastname: Olivenstein
authors.forename: J G
authors.initials: JG
authors.lastname: Martin
mesh_terms: D000336:Aerosols; D000485:Allergens / Q000276:immunology; D000818:Animals; D000941:Antigens / Q000276:immunology*; D001991:Bronchitis / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology; D003907:Dexamethasone / Q000494:pharmacology / Q000627:therapeutic use*; D007114:Immunization; D008168:Lung / Q000166:cytology / Q000187:drug effects / Q000503:physiopathology; D016131:Lymphocyte Subsets / Q000187:drug effects; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
chemical_list: D000336:Aerosols; D000485:Allergens; D000941:Antigens; D016210:Methacholine Chloride; D003907:Dexamethasone