Mast cells in the laryngeal mucosa of the rat. Effect of compound 48/80 and dexamethasone: a quantitative and immunohistochemical study at the light- and electron-microscopic levels.

Mucosal mast cells (MMCs) and connective tissue mast cells (CTMCs) in the epiglottic and subglottic regions in the rat larynx were characterized and quantified by immunohistochemistry and by light and electron microscopy, in control rats and rats injected intraperitoneally with dexamethasone and compound 48/80. Considerable regional differences were observed in the distribution of mast cells, especially in the epiglottis, where most cells were located on the laryngeal side. In the epithelium of the subglottic region the MMCs showed immunoreactivity for 5-hydroxytryptamine, in contrast to the epithelial MMCs in the epiglottis. In ultrathin sections, the subglottic MMCs contained larger but fewer granules compared with the epiglottic MMCs. After treatment with dexamethasone, the MMCs in the epithelium disappeared, while after treatment with compound 48/80 a large number of the CTMCs in the lamina propria became degranulated, though still present. This study shows that MMCs in the epiglottic and subglottic regions may be of two subtypes, differing in number and size of the granules as well as in chemical content.