title: What evidence implicates airway smooth muscle in the cause of BHR?
abstract: Bronchial hyperresponsiveness (BHR), the occurrence of excessive bronchoconstriction in response to relatively small constrictor stimuli, is a cardinal feature of asthma. Here, we consider the role that airway smooth muscle might play in the generation of BHR. The weight of evidence suggests that smooth muscle isolated from asthmatic tissues exhibits normal sensitivity to constrictor agonists when studied during isometric contraction, but the increased muscle mass within asthmatic airways might generate more total force than the lesser amount of muscle found in normal bronchi. Another salient difference between asthmatic and normal individuals lies in the effect of deep inhalation (DI) on bronchoconstriction. DI often substantially reverses induced bronchoconstriction in normals, while it often has much less effect on spontaneous or induced bronchoconstriction in asthmatics. It has been proposed that abnormal dynamic aspects of airway smooth muscle contraction velocity of contraction or plasticity- elasticity balance might underlie the abnormal DI response in asthma. We suggest a speculative model in which abnormally long actin filaments might account for abnormally increased elasticity of contracted airway smooth muscle.
authors.affiliation: Department of Medicine, University of Chicago, IL, USA.
authors.forename: Nickolai O
authors.initials: NO
authors.lastname: Dulin
authors.forename: Darren J
authors.initials: DJ
authors.lastname: Fernandes
authors.forename: Maria
authors.initials: M
authors.lastname: Dowell
authors.forename: Shashi
authors.initials: S
authors.lastname: Bellam
authors.forename: John
authors.initials: J
authors.lastname: McConville
authors.forename: Oren
authors.initials: O
authors.lastname: Lakser
authors.forename: Richard
authors.initials: R
authors.lastname: Mitchell
authors.forename: Blanca
authors.initials: B
authors.lastname: Camoretti-Mercado
authors.forename: Paul
authors.initials: P
authors.lastname: Kogut
authors.forename: Julian
authors.initials: J
authors.lastname: Solway
mesh_terms: D000199:Actins / Q000502:physiology; D000818:Animals; D001249:Asthma / Q000503:physiopathology*; D001980:Bronchi / Q000187:drug effects / Q000503:physiopathology*; D016535:Bronchial Hyperreactivity / Q000503:physiopathology*; D016085:Bronchoconstrictor Agents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004548:Elasticity; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D016210:Methacholine Chloride / Q000494:pharmacology; D009130:Muscle, Smooth / Q000503:physiopathology*; D012119:Respiration
chemical_list: D000199:Actins; D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride; D006632:Histamine