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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: BACKGROUND, METHODS, RESULTS. Meshes: Adult, Airway Resistance, Bradykinin, Double-Blind Method, Female, Humans, Male, NG-Nitroarginine Methyl Ester, Nasal Obstruction, Nasal Provocation Tests, Nitric Oxide, Nitric Oxide Synthase, Platelet Activating Factor.
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Is the effect of platelet-activating factor ( PAF ) on nasal airway resistance in healthy subjects mediated by nitric oxide? Context: The nose is an important source of nitric oxide (NO) in man, but the relevance of NO production to the response to inflammatory mediators is not clear. In this study, we evaluated the effect of NO inhibition on nasal airway resistance (NAR) at baseline, after an acute challenge with platelet-activating factor (PAF), a potent proinflammatory factor, and after an acute challenge with bradykinin (BK), both of which are mediators of allergic rhinitis in man. Eight healthy subjects were enrolled in the study. Nasal NO production was measured by the chemiluminescence method, and NAR was measured by active anterior rhinomanometry. Basal nasal NO concentration was 500.6+/-115.6 ppb; it significantly decreased after topical administration of the NO-synthase inhibitor L-NAME, and the NO-synthase substrate L-arginine caused a recovery in NO production. The administration of L-NAME did not cause any change in basal NAR. In a double-blind fashion, we performed nasal challenge with PAF and BK after topical pretreatment with either placebo or L-NAME. After placebo pretreatment, both PAF and BK caused a significant increase in NAR (respectively, from 0.29+/-0.11 Pa s cm(-3) to 0.75+/-0.21 Pa s cm(-3), and from 0.36+/-0.18 Pa s cm(-3) to 0.71+/-0.25 Pa s cm(-3); P<0.001, n=8). Pretreatment with L-NAME did not prevent the PAF-induced increase in NAR (from 0.31+/-0.10 Pa s cm(-3) to 0.71+/-0.27 Pa s cm(-3)), whereas it prevented the BK-induced increase in NAR (from 0.33+/-0.15 Pa s cm(-3) to 0.43+/-0.16 Pa s cm(-3)).
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Topical administration of the NO-synthase inhibitor L-NAME at doses sufficient to decrease NO nasal production does not prevent the PAF-induced increase in NAR, indicating that NO generation in vivo is not involved in the nasal response to PAF. Final Decision: no