Structure and function of mucus-secreting cells of cat and goose airway epithelium

In the cat and goose, studies have been undertaken to determine the ultrastructure of airway epithelia, the concentration and distribution of the secretory cells which produce respiratory tract mucus, and the histochemistry of mucins located within cells and on their luminal surfaces. By electron microscopy all the 11 cell types so far described can be found in the airways of the cat but not the goose. Both goblet cells and submucosal glands are abundant in the cat whereas the trachea of goose lacks the latter, having instead abundant goblet cells many of which form 'intraepithelial glands'. Histochemically, the goblet cells of the cat and goose are similar in that they contain mucins with a predominance of sulphate esters. A surface mucosubstance can be demonstrated which, histochemically, is similar to that described in dog and man. Interestingly, this surface layer may be sloughed in response to an inhaled irritant such as ammonia and thereby contribute to the respiratory tract mucus recovered experimentally. Incorporation into macromolecules of radioactively labelled mucin precursors is assessed by autoradiography of tissue sections, and preliminary results of experiments designed to test the response of mucus-secreting cells to airway irritation and the parasympathomimetic drug, pilocarpine, are also presented.