The roles of mediators, irritants and allergens in causing mucin secretion from the trachea

Two species, the cat and the goose, have been investigated to determine whether a variety of pharmacological mediators, irritants and allergens change the rate at which mucins (mucus glycoproteins) are secreted into the trachea. Mucins were labelled by the administration of radioactive precursors which the mucous cells took up and incorporated into glycoproteins. These were periodically washed out of a segment of trachea with physiological saline solution. Changes in the amount of mucin secreted were estimated from measurements of the amount of bound radioactivity in tracheal washings. Histamine increased mucin secretion but the effects were stronger and more consistent in the goose than in the cat. A variety of prostaglandins increased the secretion in both species. 5-Hydroxytryptamine failed to stimulate mucin output in the cat. Ammonia and cigarette smoke both increased mucin secretion in the cat and preliminary results suggest that this was by a combination of local and reflex mechanisms. O-Chlorobenzilidine malononitrile increased secretion from the goose trachea entirely by a local mechanism. Preliminary experiments in which sensitized cats were challenged by various routes have equivocal results on whether anaphylaxis increases airway mucin secretion. It is concluded that irritants cause mucin secretion both by reflexes and local mechanisms. The mechanisms for the latter may well include release of pharmacological mediators.