title: Conservation of bronchiolar wall area during constriction and dilation of human airways.
abstract: We assessed the effect of smooth muscle contraction and relaxation on airway lumen subtended by the internal perimeter (Ai) and total cross-sectional area (Ao) of human bronchial explants in the absence of the potential lung tethering forces of alveolar tissue to test the hypothesis that bronchoconstriction results in a comparable change of Ai and Ao. Luminal area (i.e., Ai) and Ao were measured by using computerized videomicrometry, and bronchial wall area was calculated accordingly. Images on videotape were captured; areas were outlined, and data were expressed as internal pixel number by using imaging software. Bronchial rings were dissected in 1.0- to 1.5-mm sections from macroscopically unaffected areas of lungs from patients undergoing resection for carcinoma, placed in microplate wells containing buffered saline, and allowed to equilibrate for 1 h. Baseline, Ao [5.21 +/- 0.354 (SE) mm2], and Ai (0.604 +/- 0.057 mm2) were measured before contraction of the airway smooth muscle (ASM) with carbachol. Mean Ai narrowed by 0.257 +/- 0.052 mm2 in response to 10 microM carbachol (P = 0.001 vs. baseline). Similarly, Ao narrowed by 0.272 +/- 0.110 mm2 in response to carbachol (P = 0.038 vs. baseline; P = 0.849 vs. change in Ai). Similar parallel changes in cross-sectional area for Ai and Ao were observed for relaxation of ASM from inherent tone of other bronchial rings in response to 10 microM isoproterenol. We demonstrate a unique characteristic of human ASM; i.e., both luminal and total cross-sectional area of human airways change similarly on contraction and relaxation in vitro, resulting in a conservation of bronchiolar wall area with bronchoconstriction and dilation.
authors.affiliation: Department of Medicine, University of Chicago, Illinois 60637, USA.
authors.forename: R W
authors.initials: RW
authors.lastname: Mitchell
authors.forename: E
authors.initials: E
authors.lastname: Rühlmann
authors.forename: H
authors.initials: H
authors.lastname: Magnussen
authors.forename: N M
authors.initials: NM
authors.lastname: Muñoz
authors.forename: A R
authors.initials: AR
authors.lastname: Leff
authors.forename: K F
authors.initials: KF
authors.lastname: Rabe
mesh_terms: D001980:Bronchi / Q000502:physiology*; D016084:Bronchoconstriction / Q000502:physiology; D006801:Humans; D009126:Muscle Relaxation / Q000502:physiology*; D012132:Respiratory Muscles / Q000502:physiology*