The site of methacholine reactivity in the peripheral airways:
analysis using lung explants.
Wright, J. L., J. P. Sun, Andrew Churg.
University of British Columbia
APStracts 3:0141L, 1996.
We utilized a recently developed lung explant technique to investigate
the partitioning of airway contractility in the bronchioles of
normoresponsive and hyperresponsive rats. Specifically, we addressed
the questions: 1) whether airway response to methacholine varied with
airway size; and 2) whether airways from rats known to be innately
hyperresponsive to methacholine (Fisher) would have responses
different from normoresponsive rats (Sprague Dawley). We found that,
in both strains of rat, contraction to methacholine occurred
primarily in the medium and larger sized bronchioles (airways of
diameter >.32mm), and that, at the higher [Mch] the Fisher rats
had greater degrees of contraction than did the Sprague-Dawley rats.
These results suggest that the increased airways responsiveness seen
in Fisher rats is due to an intrinsic increase in responsiveness
(increased contractility) of their airways which may be related to
amount of smooth muscle, rather than an increase in airway
sensitivity to methacholine. They do not, however, completely rule
out the possibility of in vivo species dependent differences in
airway-parenchymal interactions.
Received 27 March 1996; accepted in final form 19 August 1996.
APS Manuscript Number L101-6.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996