title: Airway hyperresponsiveness in allergically inflamed mice: the role of airway closure.
abstract: BACKGROUND
  Allergically inflamed mice exhibit airway hyperresponsiveness to inhaled methacholine, which computer simulations of lung impedance suggest is due to enhanced lung derecruitment and which we sought to verify in the present study.
  
  
  METHODS
  BALB/c mice were sensitized and challenged with ovalbumin to induce allergic inflammation; the control mice were sensitized but received no challenge. The mice were then challenged with inhaled methacholine and respiratory system impedance tracked for the following 10 minutes. Respiratory elastance (H) was estimated from each impedance measurement. One group of mice was ventilated with 100% O(2) during this procedure and another group was ventilated with air. After the procedure, the mice were killed and ventilated with pure N(2), after which the trachea was tied off and the lungs were imaged with micro-computed tomography (micro-CT).
  
  
  RESULTS
  H was significantly higher in allergic mice than in control animals after methacholine challenge. The ratio of H at the end of the measurement period between allergic and nonallergic mice ventilated with O(2) was 1.36, indicating substantial derecruitment in the allergic animals. The ratio between lung volumes determined by micro-CT in the control and the allergic mice was also 1.36, indicative of a corresponding volume loss due to absorption atelectasis. Micro-CT images and histograms of Hounsfield units from the lungs also showed increased volume loss in the allergic mice compared with control animals after methacholine challenge.
  
  
  CONCLUSIONS
  These results support the conclusion that airway closure is a major component of hyperresponsiveness in allergically inflamed mice.
authors.affiliation: Vermont Lung Center, The University of Vermont College of Medicine, HSRF 230, 149 Beaumont Avenue, Burlington, VT 05405-0075, USA. lennart.lundblad@uvm.edu
authors.forename: Lennart K A
authors.initials: LK
authors.lastname: Lundblad
authors.forename: John
authors.initials: J
authors.lastname: Thompson-Figueroa
authors.forename: Gilman B
authors.initials: GB
authors.lastname: Allen
authors.forename: Lisa
authors.initials: L
authors.lastname: Rinaldi
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Norton
authors.forename: Charles G
authors.initials: CG
authors.lastname: Irvin
authors.forename: Jason H T
authors.initials: JH
authors.lastname: Bates
mesh_terms: D000818:Animals; D016535:Bronchial Hyperreactivity / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology*; D001985:Bronchial Provocation Tests; D005260:Female; D008176:Lung Volume Measurements; D051379:Mice; D008807:Mice, Inbred BALB C; D001261:Pulmonary Atelectasis / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology*; D012121:Respiration, Artificial; D012130:Respiratory Hypersensitivity / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology*; D014057:Tomography, X-Ray Computed