Influence of Pilocarpine and Ammonia Vapour on the Secretion and Structure of Cat Tracheal Mucins: Differentiation of Goblet and Submucosal Gland Cell Secretions

Abstract

The visco-elastic properties of epithelial mucus, essential to its physiological role as a lubricative and protective layer, are derived from its glycoprotein components. It is clear therefore that the precise regulation of the production and clearance of mucus is a basic requirement to the maintenance of a healthy epithelial mucosa. Our work has been mainly concerned with the control of mucus secretion in the tracheae of anaesthetised cats in which we showed that stimulation of both sympathetic and parasympathetic nerves could significantly increase mucus output (Gallagher, et al., 1975). The parasympathetic effect could be reproduced by pilocarpine, which was effective when given into the tracheal lumen, thus overcoming systemic effects when the drug was administered intravenously. Radioautography of ³⁵S-sulphate-labelled mucins indicated that pilocarpine and nervous stimuli were causing the release of mucus from submucosal glands (both serous and mucous glands) rather than from surface epithelial goblet cells. Gland cell mucus also appeared to be more sulphated than the mucus in goblet cells. In contrast, respiratory irritants such as dilute mustard oil (Florey, et al., 1932) and ammonia vapour (R. Phipps, P. Richardson and O. Jeffery, unpublished observations) promote secretion from both goblet and gland cells. In an attempt to examine structural and metabolic differences between goblet and gland cell mucins we have used pilocarpine to release submucosal gland cell mucins and then applied ammonia vapour to the same tracheae to promote secretion from goblet cells.