DO NASAL MAST-CELLS RELEASE HISTAMINE ON STIMULATION WITH SUBSTANCE-PIN ALLERGIC RHINITIS

The effects of nasal administration of increasing doses of exogenous s ubstance P have been studied in patients with allergic rhinitis treate d with placebo or with the H-1 antagonist cetirizine (10 mg twice dail y for 3 days). Responses to substance P were assessed by posterior rhi nomanometry (measuring nasal airway resistance) and by measure of hist amine, protein and albumin production and cell recovery in nasal ravag e fluids before and after challenge. Substance P induced a dose-depend ent increase in nasal airway resistance which was similar after treatm ent with either cetirizine or placebo (maximal increase in nasal airwa y resistance was 4.2-fold greater than the baseline with the placebo a nd 4.7-fold greater than the baseline with cetirizine). No histamine r elease was observed. Similar increases in protein and albumin producti on were observed after stimulation with substance P along with the pla cebo (protein: from 0.35+/-0.11 to 3.31+/-0.62 mg and albumin: from 0. 09+/-0.04 to 2.08+/-0.39 mg) and when combined with cetirizine treatme nt (proteins: from 0.42+/-0.09 to 3.62+/-0.77 and albumin: from 0.17+/ -0.04 to 2.19+/-0.51 mg). After stimulation with substance P, percenta ges of neutrophils recovered in nasal fluids increased from 26.2+/-11. 5 to 54.5+/-9.5 with the placebo and from 35.5+/-11.0 to 53.6+/-9.5 wi th cetirizine. Eosinophils were inconsistently found after substance P stimulation during both treatments. In conclusion, nasal response to substance P is not modified by cetirizine which suggests that the effe ct of substance P is not secondary to histamine release in the nose in man.