Neuropeptides and airway submucosal gland secretion.

Our study using feline tracheal isolated submucosal gland preparation has revealed that substance P (SP) produces an increase in submucosal gland secretion through the actions of both mucus ejection by glandular contraction and macromolecule secretion from secretory cells, and that the two actions are both mediated by a peripheral cholinergic action. In contrast, SP has no significant effect on macromolecule secretion from secretory cells in tracheal explants, probably because of epithelial suppression. Our study using an isolated gland preparation has also indicated that VIP potentiates mucous glycoprotein secretion induced by cholinergic stimulation through an interaction between muscarinic and VIP receptors in secretory cells. However, VIP failed to induce any significant glandular contraction or relaxation, indicating a lack of VIP receptors or a difference in the subtypes of muscarinic receptors in myoepithelial cells in submucosa glands.