title: Consecutive allergen challenges resulted in decreased bronchial responsiveness.
abstract: OBJECTIVE
  To investigate bronchial responsiveness to acetylcholine in allergic airway inflammation of SD rats.
  
  
  METHODS
  SD rats were immunized and challenged by chicken ovalbumin (OVA). Airway responsiveness, acetylcholine (Ach) provocation concentration needed to increase baseline airway resistance by 200% (PC(200)) were measured.
  
  
  RESULTS
  The value of baseline airway resistance in asthma group was significantly higher than that in control group (2.282 +/- 0.128 vs 3.193 +/- 0.239; P < 0.01). After multiple ovalbumin exposures, airway responsiveness to intravenous injection of acetylcholine decreased significantly (-LogPC(200): 4.006 +/- 0.554 vs 2.059 +/- 0.262; P < 0.01). Bronchial alveolar lavage fluid (BALF) and lung tissue specimen analysis indicated that airway allergic inflammation was present.
  
  
  CONCLUSIONS
  The study demonstrates a dissociation between the bronchoconstrictor response and bronchial hyper-responsiveness and indicates that multiple ovalbumin exposures induces persistent bronchoconstriction with airway hypo-responsiveness despite airway allergic inflammation.
authors.affiliation: Respiratory Department, Beijing Children's Hospital, Capital University of Medical Sciences, Beijing 100045, China.
authors.forename: Jianxin
authors.initials: J
authors.lastname: He
authors.forename: Zaifang
authors.initials: Z
authors.lastname: Jiang
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000403:Airway Resistance; D000485:Allergens / Q000276:immunology*; D000818:Animals; D001980:Bronchi / Q000187:drug effects / Q000502:physiology; D016535:Bronchial Hyperreactivity / Q000209:etiology*; D016084:Bronchoconstriction; D008168:Lung / Q000473:pathology; D008297:Male; D010047:Ovalbumin / Q000276:immunology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000485:Allergens; D010047:Ovalbumin; D000109:Acetylcholine