We studied the effects of antigen aerosol challenge on the airways of the canine peripheral lung and examined the roles of cyclooxygenase products, histamine, and cholinergic activity in the responses. One-minute deliveries of 1:10,000 or 1:100,000 concentrations of Ascaris suum antigen aerosol through a wedged bronchoscope resulted in mean maximal increases in collateral system resistance (Rcs) of 415 and 177%, respectively, after 4-8 min. Repeated antigen challenge (1:100,000) resulted in significantly decreased responsiveness to antigen after the initial exposure (P < 0.005). Bronchoalveolar lavage fluid obtained from the isolated, challenged segment had a significant increase in mean (± SE) prostaglandin D2 (PGD2) concentration vs. control (222.0 ± 65.3 vs. 72.7 ± 19.5 pg/ml; P < 0.05); histamine concentrations were variable and not significantly different (4.1 ± 2.6 vs. 1.2 ± 0.2 ng/ml; P > 0.05). In nine experiments, cyclooxygenase inhibition significantly attenuated the antigen-induced increase in Rcs by 53.4% (P < 0.001), and the concentration of PGD2 in lavage fluid was reduced by 96.0% (P < 0.01). Blockade of histamine H1-receptors (n = 8) or cholinergic receptors (n = 7) did not significantly affect the airway response (P > 0.05). These data indicate that the canine peripheral lung responds in a dose-dependent manner to antigen aerosol challenge and exhibits characteristics of antigen tachyphylaxis. Results also suggest that cyclooxygenase products play a central role in the acute bronchoconstrictive response of the lung periphery.
ASJC Scopus subject areas
- Physiology (medical)