Pathophysiology of rhinitis. 1. Assessment of the sources of protein in methacholine-induced nasal secretions.

Nasal provocation tests with normal saline and methacholine (MC) were performed in 25 atopic and 27 nonatopic subjects in an effort to assess the sources of protein in induced airway secretions. Nasal lavages obtained at baseline and after provocation were analyzed for albumin, total protein, secretory IgA (sIgA), and total IgA. Compared with baseline levels or saline provocation, MC provocation increased the secretion of albumin (p less than 0.025), total protein (p less than 0.001), sIgA (p less than 0.025), and total IgA (p less than 0.025), but did not significantly affect the relative proportions of albumin-to-total protein (albumin percent) or sIgA-to-total IgA (sIgA/total IgA ratio). Nasal pretreatment with atropine significantly inhibited MC-induced secretion of all 4 proteins, again without affecting the albumin percent or the sIgA/total IgA ratio. Because MC is known to stimulate atropine-inhibitable secretion of glandular products, these data suggest that sIgA and albumin may accompany glandular secretions. Immunohistochemical analyses of nasal turbinates confirmed that secretory component was found only on serous cells within submucous glands. Thus, it appears that cholinergic stimulation may regulate sIgA secretion and thereby participate in local nasal (and possibly respiratory tract) immunity.