Rat sublingual gland as a model to study glandular mucous cell secretion

To study the regulation of mucous cell secretion, we have developed an in vitro cell model consisting of enzymatically dispersed mucous acinar structures (cell aggregates) from rat sublingual glands. Histological and ultrastructural evidence demonstrates that the cell aggregates are highly enriched in mucous cells, retain the morphological and ultrastructural features observed in intact glands, and undergo transition to an extensive secretory state when stimulated by 10 microM carbachol. The secretory responsiveness of the cell aggregates was verified in pharmacological studies. Carbachol stimulated secretion in a dose-dependent manner with high affinity (concentration causing half-maximal response = 0.3 microM) and was completely inhibited by atropine. Secretion was also stimulated by vasoactive intestinal peptide and substance P but not by alpha- or beta-adrenergic agonists. Biochemical characterization of secretion during nonstimulated and carbachol-stimulated conditions (after preincubation in [3H]glucosamine) demonstrated that, in response to carbachol, cell aggregates synthesized and secreted mucins which were similar to mucin glycoproteins isolated from whole glands. Collectively, our results establish that the rat sublingual cell aggregate model is a viable and pharmacologically responsive cell system to study the regulation of mucous cell secretion.