Study of the effects of paf-acether on human nasal airways

In 6 normal subjects and 6 patients with allergic rhinitis, nasal response to insufflation of paf-acether (paf, platelet-activating factor), lyso-paf and histamine was evaluated. Nasal challenge with paf, at doses of 300 and 600 nM, induced nasal obstruction, associated with an increase in nasal airway resistance, measured by anterior passive rhinomanometry. Maximum increase in nasal airway resistance was observed at 30 min after challenge (mean percent change +481 with 600 nM paf; P <0.05). Other symptoms induced by paf insufflation were rhinorrhea (6 out of 12 subjects), itching (8 out of 12), sneezing (4 out of 12) and a burning sensation (6 out of 12). No differences were observed between normal and rhinitic subjects, concerning nasal sensitivity to paf. Neither nasal symptoms nor changes in nasal airway resistance were observed after nasal challenge with lyso-paf (300 and 600 nM); by contrast, histamine (100 nM) induced sneezing, nasal obstruction, itching and rhinorrhea in all the studied subjects, associated with an increase in nasal airway resistance (maximum 5 min after challenge; percent change +358; P <0.02). Nasal effects of paf were not mediated by histamine, since no increase in histamine levels was observed in nasal washings following paf insufflation. We conclude that paf may have pathogenetic relevance in allergic rhinitis.