Conservation of bronchiolar wall area during constriction and
dilation of human airways.
Mitchell, R. W., E. R[umlaut]uhlmann, H. Magnussen, N. M.
Mu[tilde]noz, A. R. Leff, and K. F. Rabe.
Asthma, Allergy, and Immunological Disease Cooperative Research
Center, Section of Pulmonary and Critical Care Medicine, Department
of Medicine, and the Committees on Clinical Pharmacology, Cell
Physiology, and Comparative Medicine and Pathology, Division of the
Biological Sciences, The University of Chicago, Chicago, IL 60637 and
Krankenhaus Gro[beta]hansdorf, Zentrum f[umlaut]ur Pneumologie und
Thoraxchirurgie, LVA Hamburg, D-22927 Gro[beta]hansdorf, Germany.
APStracts 3:0529A, 1996.
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. Lumenal area (Ai) and Ao were measured 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 using imaging software. Bronchial
rings were dissected in 1.0-1.5 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 hr. Baseline, Ao (5.21 +/- 0.354 (S.E.)
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 [mu]M 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 [mu]M isoproterenol. We demonstrate a unique
characteristic of human ASM, i.e., both lumenal and total cross
-sectional area of human airways change similarly upon contraction and
relaxation in vitro resulting in a conservation of bronchiolar wall
area with bronchoconstriction and dilation.
Received 22 April 1996; accepted in final form 5 November 1996.
APS Manuscript Number A385-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996