SELECTIVE RECRUITMENT OF EOSINOPHILS BY SUBSTANCE-P AFTER REPEATED ALLERGEN EXPOSURE IN ALLERGIC RHINITIS

We have investigated the nasal response to substance P after pollen ex posure in seasonal allergic rhinitic patients. Seven patients with str ictly seasonal allergic rhinitis were studied during the pollen season , 24 h after nasal challenge with pollen. They received increasing dos es of nebulized substance P (0 to 80 nmol) in each nostril. Responses were assessed by measurement of nasal airway resistance by posterior r hinomanometry and quantification of albumin, histamine, and inflammato ry cells in the nasal lavage fluid. Nasal airway resistance increased in a dose-dependent manner after substance P challenge. Protein and al bumin in nasal lavage fluids increased after administration of substan ce P: from 2.6 +/- 0.3 to 6.8 +/- 1.1 mg for protein (P<0.01) and from 0.2 +/- 0.1 to 3.1 +/- 0.6 mg for albumin (P<0.02). Expressed as a pe rcentage of total protein, albumin increased from 10.5 +/- 3.6% to 39. 9+/-3.5% (P<0.02), suggesting occurrence of plasma leakage. No histami ne release was observed after challenge with substance P. Total cell c ounts significantly increased from 11.4 +/- 2.4 to 41.8 +/- 17.3 x 10( 3) cells/ml after substance P (P<0.05). Eosinophils were already numer ous before substance P challenge (2.1 +/- 0.7 x 10(3) cells/ml), and t he number of eosinophils markedly increased in all patients after subs tance P (for the whole group, 25.8 +/- 13.3 cells/ml, P<0.05). In cont rast, the number of neutrophils only slightly increased in five patien ts, and changes did not reach significance for the group as a whole. O ur results show that substance P induces nasal obstruction and albumin extrusion in allergic rhinitic patients after repeated pollen exposur e. These vascular phenomena are associated with recruitment of eosinop hils. Since substance P is known to be released after nasal allergen c hallenge, our data suggest a role for substance P in the chronic eosin ophilic inflammation of the nasal mucosa observed in symptomatic aller gic rhinitis.