Journal of Applied Physiology, Vol 65, Issue 3 1238-1243, Copyright © 1988 by American Physiological Society
Release of epithelium-derived relaxing factor after ozone inhalation in dogs
G. L. Jones, C. G. Lane, E. E. Daniel and P. M. O'Byrne
Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
Airway epithelium has been reported to release epithelium-derived relaxing
factor (EpDRF), which inhibits contraction of airway smooth muscle. This
study tested the hypothesis that airway hyperresponsiveness after
inhalation of ozone in dogs results from an inability to produce EpDRF. Two
groups of five dogs each were studied; one group inhaled ozone, the other
dry room air. Ozone-treated dogs developed airway hyperresponsiveness,
whereas the control group did not. The acetylcholine provocative
concentration decreased from 4.17 (%SE 1.35) to 0.56 mg/ml (%SE 1.24) (P =
0.0006) in the ozone-treated dogs and was 18.76 (%SE 2.04) and 29.77 mg/ml
(%SE 2.07) in the air-treated dogs (P = 0.47). In vitro the presence of
airway epithelium reduced the constrictor responses to acetylcholine,
histamine, serotonin, and KCl in trachealis strips from the control dogs.
This effect of epithelium was still present in trachealis strips from dogs
with airway hyperresponsiveness. These results demonstrate that EpDRF is
released from canine tracheal epithelium, that this function is not
impaired in dogs with airway hyperresponsiveness after inhaled ozone, and
that loss of EpDRF is not responsible for the development of airway
hyperresponsiveness after inhaled ozone in dogs.
