Airway secretions form a protective barrier over the airway epithelium which participates in mucociliary transport to clear inhaled pathogens from the airways. Important parts of this barrier, called mucus, are mucous glycoproteins, lipids, and other proteins which interact to impart viscoelastic properties of mucus necessary for normal mucociliary transport. Changes in the quantity or chemical composition of these components, especially mucous glycoproteins, may alter mucociliary clearance whose failure is associated with many pulmonary diseases. The source of these components include secretory cells of the surface epithelium, airway submucosal glands and serum transudates. Of these sources, the submucosal glands are thought to contribute the largest share. However, little is known of the specific secretory products of gland cells or secretagogue- induced changes in the quantity or chemical composition of specific cell secretions. This is because past studies used whole tissue in vivo and in vitro, which contains multiple cell types. To study gland cell secretory products and the regulation of their secretion, we have developed techniques to isolate and culture cat tracheal gland cells in primary culture. Preliminary data indicate these cells are viable, secrete mucous glycoproteins, and respond to cholinergic agonists. This cell system provides a unique model to study a glandular secretory cell without interference from other cellular, neuronal, connective tissue or blood-borne factors. We plan to use primary cultures of gland cells to: 1) determine the secretory contributions of glandular cells during basal secretion; 2) determine the profile of pre- formed secretory components released during acute secretagogue stimulation; and 3) determine the profile of secretory components released during chronic exposure to secretagogue. In particular, we will concentrate on identifying specific high-molecular weight proteoglycans and characterizing secreted mucous glycoproteins. Also, lower molecular weight species will be surveyed. The results from these studies will provide a framework of data upon which to build a better understanding of the specific cellular contributions to components of mucus and how these components interact and are regulated to ultimately help control mucociliary transport.
