Effect of c-fiber mediated, ozone-induced rapid shallow breathing on the distribution
of airway epithelial injury in the rat.
Schelegle, E. S., M. F. Alfaro, L. Putney, M. Stovall, N. Tyler, and D. M. Hyde.
Department of Anatomy, Physiology and Cell Biology, School of Veterinary
Medicine, University of California, Davis, California 95616
APStracts 8:0333A, 2001.
We examined the relationship between C-fiber mediated, ozone-induced rapid shallow
breathing and airway epithelial cell injury at different airway sites within the lower
respiratory tract of conscious Wistar rats (n = 24). We combined an acute 8-h ozone
inhalation with vagal perineural capsaicin treatment, a selective C-fiber conduction block,
and 5-bromo-2-deoxyuridine (BrdU) labeling as an index of epithelial injury. Vehicle-
treated rats that inhaled ozone developed a rapid shallow breathing pattern during ozone
inhalation, whereas the capsaicin-treated rats that inhaled ozone showed no changes in
breathing frequency. In vehicle-treated, ozone-exposed rats that developed rapid shallow
breathing, a progressive increase in BrdU-labeling density (no. of BrdU-labeled
cells/mm2 airway) was observed starting at the bifurcation of the left main stem bronchi
(central airway) and going down either a short or long airway path. In vehicle-treated,
ozone-exposed rats terminal bronchioles supplied by short and long airway paths had a
similar degree of BrdU-labeling density, that was significantly (P < 0.05) greater than
the BrdU-labeling density of the proximal airways that supply them. In contrast, the
attenuation of rapid shallow breathing produced by capsaicin treatment resulted in a
significantly reduced BrdU-labeling density in the terminal bronchioles supplied by short
airway paths compared with the terminal bronchioles supplied by long airway paths. Our
data indicate that ozone-induced rapid shallow breathing protects large conducting
airways while producing a more even distribution of injury to terminal bronchioles.
Received 30 November 2000; accepted in final form 24 May 2001
APS Manuscript Number A1,159-0.
Article publication pending J Appl Physiol
ISSN 1080-4757 Copyright 2001 The American Physiological Society.
Published in APStracts on 29 June 2001