Comparison of human nasal mucosal secretion in vivo and in vitro

The secretion of proteins from the human nasal mucosa induced by histamine, alpha-adrenergic, beta-adrenergic, and cholinergic agonists was studied in vivo and in vitro. Glandular secretion of lactoferrin, lysozyme (in vivo only), and respiratory glycoconjugates (RGCs) was measured. Vascular permeability was determined in vivo by albumin secretion in relationship to the other proteins. Muscarinic stimulation by methacholine induced significant glandular secretion (lactoferrin, lysozyme and/or RCGs) both in vivo and in vitro, confirming that muscarinic receptors are stimulated directly. Histamine induced predominantly vascular permeability in vivo but caused some glandular secretion as well. However, in vitro, histamine had no effect on glandular secretion, suggesting that histamine acts predominantly on the nasal vascular bed and only affects glandular secretion through reflex actions. Phenylephrine, an alpha-adrenergic agonist, selectively stimulated lysozyme release in vivo, and both RGCs and lactoferrin release in vitro. Thus, alpha-adrenergic stimulation has some direct, albeit minimal, capacity to stimulate mucosal glands. beta-Adrenergic agonists had no effect on glandular secretion or vascular permeability either in vivo or in vitro. Therefore, glandular secretion is directly stimulated by alpha-adrenergic and cholinergic agonists, but not by beta-adrenergic agonists. The stimulation of glandular secretion by histamine is indirect and mediated through the action of neural reflexes.