Tracheal mucous transport in experimental canine asthma

Tracheal mucous velocity (TMV) was measured in experimental canine asthma. All 10 sensitive dogs exposed to an aerosol of Ascaris suum extract showed a decrease in TMV to about one-third of base-line values within 45 min whereas only half of them (reactors) responded with bronchospasm as measured by a significant reduction in specific respiratory system conductance (SGrs). Mean TMV remained decreased at the end of the 2-h observation period when mean SGrs had returned to base-line values in the reactors. Neither TMV nor SGrs changed in nonsensitive animals who inhaled ragweed antigen. Aerosols of acetylcholine and histamine increased TMV thereby excluding these mediators as responsible for the impairment of mucous transport in asthma. Nebulization of A. suum antigen together with a selective antagonist of slow reacting substance of anaphylaxis (srs-a) produced a marked increase of TMV in all dogs regardless of whether or not bronchospasm was elicited. This suggests that the observed decrease in TMV may be related to the release of SRS-A during the immunologic reaction.