Airway wall dimensions during carbachol-induced bronchoconstriction
in rabbits.
Sasaki, F., Y. Saitoh, L. Verburgt, and M. Okazawa.
Respiratory Health Network of Center of Excellence, University of
British Columbia, Pulmonary Research Laboratory, St. Paul's Hospital,
Vancouver, B.C. V6Z 1Y6, Canada
APStracts 3:0290A, 1996.
Airway wall area is an important determinant of airway narrowing. We
hypothesized that in cross-sectioned peripheral airways, the wall
area internal to the outer smooth muscle border (inner wall area)
would decrease and the airway wall area external to the outer smooth
the muscle layer (adventitial area) would increase during
bronchoconstriction because of the relocation of blood and/or fluid
between these compartments. To test this hypothesis, we used
anesthetized open chest rabbits and measured airway wall dimensions
and smooth muscle shortening of membranous airways after carbachol
induced bronchoconstriction using morphometric techniques. Acute (3
minutes) and sustained (40 minutes) bronchoconstriction was induced
by aerosol nebulization of carbachol and compared with saline
treatment. Following physiologic measurements, the heart base was
snared and the lung and heart were excised en bloc and frozen using
liquid nitrogen maintaining a transpulmonary pressure of 2 cmH2O. The
lung was processed for light microscopic examination using a freeze
substitution technique. Results show that adventitial area was
significantly decreased following sustained but not acute
bronchoconstriction. The mechanism of this change, which contradicts
our hypothesis, is unclear. However, the decrease of adventitial area
could increase rather than decrease the effect of lung parenchymal
tethering and attenuate airway narrowing.
Received 22 June 1995; accepted in final form 13 May 1996.
APS Manuscript Number A666-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 28 June 96