title: The effects of age and carbon black on airway resistance in mice.
abstract: BACKGROUND
  Ambient particulate matter (PM) is associated with acute exacerbations of airflow obstruction. Additionally, elderly individuals are more susceptible to increased functional morbidity following acute PM exposure.
  
  
  OBJECTIVE
  The purpose of this study is to determine the aging effects of PM exposure on the responsiveness of airway smooth muscle in mice. We hypothesized that airway reactivity induced by methacholine (Mch) will increase with age in PM exposed mice.
  
  
  METHODS
  Male C57BL/6 (B6) mice at 11, 39, 67, and 96 weeks of age were exposed to carbon black (CB) or room air (RA) for 3 h on 3 consecutive days. One day after the last exposure, mice were anesthetized and airways resistance (R(aw)) was measured by forced oscillation following half-log dose increases of aerosolized Mch.
  
  
  RESULTS
  Baseline R(aw) was significantly lower in 67 and 96 week mice compared to 11-week mice (p < 0.05). In RA exposed mice, an age-dependent decline in Mch-induced airway reactivity occurred in association with the highest Mch doses at ages 67 and 96 weeks (p < 0.05). A significantly (p < 0.05) greater Mch-induced R(aw) response occurred in 67-week mice exposed to CB compared with age-matched RA-exposed mice.
  
  
  CONCLUSIONS
  Our results show a progressive decrease in the Mch-induced R(aw) response with age in mice. The effect of CB exposure resulted in greater airway reactivity in middle-aged mice, which highlights the effects of PM exposure on the lung as it relates to increased morbidity and mortality with older age.
authors.affiliation: Department of Environmental Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: Blake A
authors.initials: BA
authors.lastname: Bennett
authors.forename: Wayne
authors.initials: W
authors.lastname: Mitzner
authors.forename: Clarke G
authors.initials: CG
authors.lastname: Tankersley
mesh_terms: D000367:Age Factors; D000375:Aging; D000403:Airway Resistance / Q000187:drug effects*; D000818:Animals; D016535:Bronchial Hyperreactivity / Q000139:chemically induced* / Q000175:diagnosis / Q000503:physiopathology; D001985:Bronchial Provocation Tests; D016085:Bronchoconstrictor Agents; D019570:Inhalation Exposure; D008168:Lung / Q000187:drug effects* / Q000503:physiopathology; D008297:Male; D016210:Methacholine Chloride; D051379:Mice; D008810:Mice, Inbred C57BL; D009130:Muscle, Smooth / Q000187:drug effects* / Q000503:physiopathology; D052638:Particulate Matter / Q000008:administration & dosage / Q000633:toxicity*; D012307:Risk Factors; D053260:Soot / Q000008:administration & dosage / Q000633:toxicity*
chemical_list: D016085:Bronchoconstrictor Agents; D052638:Particulate Matter; D053260:Soot; D016210:Methacholine Chloride