Journal of Applied Physiology, Vol 54, Issue 4 1101-1107, Copyright © 1983 by American Physiological Society
Citric acid airway constriction in dogs with hyperreactive airways
C. A. Hirshman, J. Peters, H. Downes, D. Leon, R. K. Lynn, J. Butler and J. M. Hanifin
To understand the mechanisms underlying the bronchoconstrictor response to
10% citric acid administered for 5 min in Basenji-Greyhound (BG) dogs, we
evaluated the protection afforded by atropine (0.2 and 0.4 mg/kg iv) and by
aerosols of isoproterenol (1 mg/ml) and cromolyn sodium (20 mg/ml). In
untreated dogs, citric acid increased pulmonary resistance by 4.6- to
11.5-fold and decreased dynamic compliance (Cdyn) to 45-55% of the control
response. Isoproterenol and cromolyn sodium significantly reduced the
response, whereas atropine did not. Moreover we have demonstrated in the
arterial plasma of these dogs a slow-reacting substance (SRS) after, but
not before, citric acid challenge. This SRS exhibits both pharmacologic
properties and chemical characteristics similar to leukotrienes. We
conclude that mediators of immediate-type hypersensitivity rather than
reflex mechanisms play a dominant role in the production of airway
constriction during citric acid (5-min) challenge in BG dogs.
