The action of dust in the airways on secretion into the trachea of the cat.

The effects of inert dusts administered into cat airways on the release of radiolabelled mucus glycoproteins (mucins) from an isolated tracheal segment have been investigated. Charcoal dust or barium sulphate powder, when placed in the segment, stimulated release of both 35S- and 3H-labelled mucins. The effect of dust was not significantly reduced after denervation of the segment. Charcoal dust, when added to the inspired air, caused an increase in release of mucins labelled with both radio-isotopes. Bilateral vagotomy significantly reduced this effect, but atropine and l-propranolol administered together did not. It is concluded that inert dust can stimulate tracheal mucin output both by a local mechanism and by activation of a reflex. The types of receptor that may be involved in the reflex, and the possible role of the mucotropic effects of dust in airway clearance, are discussed.