Evaluation of secretory and transport processes which determine the composition of airway surface liquid

Abstract

Airway surface liquid has complex physical and biochemical properties, which are suited to protect the airways from damage caused by infections and irritation by particles in inhaled air. Airway epithelial cells and gland cells (serous and mucous cells) secrete and transport materials such as lysozyme, antiproteases, sulphated proteoglycans, hyaluronic acid, mucins, ions and water which determine the chemical composition and the physical properties of the mucus gel lining the airways. The quantities and nature of the transported and secreted components of airway surface liquid can be detrimentally changed as a feature of several airway diseases. Thus from a therapeutic angle there is a need to understand the control mechanisms which ultimately determine the resistance and health of the airways. In vitro animal models provide some useful approaches for investigations into cellular mechanisms of transport and secretion. Electrophysiological techniques are very valuable for studying ion transport across the surface epithelium. Additionally, cell cultures can offer a solution to overcome problems with access to gland cells [1–3]. Cell culture combined with electrophysiological techniques can extend functional studies to the single cell level and allow detailed evaluation of the mechanisms of action of pharmacological agents. In this chapter, some of the practical aspects and limitations of studying certain secretory and transport events which regulate the formation of airway surface liquid are outlined.