NASAL NITRIC-OXIDE IS INCREASED IN ALLERGIC RHINITIS

Background Nitric oxide (NO) plays a major role In the regulation of v ascular tone and in non-specific host defence. The epithelium in the p aranasal sinuses was recently identified as the major site of NO produ ction in the upper airways. Objective To investigate NO status in alle rgic rhinitis, we compared the NO concentration in the nasal cavities of control subjects (n = 19) and in patients with allergic rhinitis (n = 36) with symptoms (WS, n = 17) or without symptoms (WOS, n = 19) on the day of the test. Methods NO concentration was measured using a ch emiluminescent analyser aspiring from each nasal cavity at a sampling flow rate of 0.7 L/min, before and 10 min after administration of a na sal vasoconstrictor. Results The mean NO concentration (+/- SE) in the control was 235 +/- 11 ppb and 225 +/- 9 ppb in the right and left no strils respectively, and was decreased by 14% and 12% by the nasal vas oconstrictor (P < 0.001). The NO concentration in patients with allerg ic rhinitis was significantly higher in the right and left nostrils (3 82 +/- 20 ppb and 396 +/- 28 respectively, P < 0.0001 versus control), All WOS patients demonstrated normal or increased NO concentrations i n both nostrils, whereas two WS patients showed decreased NO concentra tions in the left nostril. Inhalation of a nasal vasoconstrictor incre ased NO concentration by 6% and 27% in the right and left nostrils res pectively in WS patients. Conclusion Nasal NO concentration is increas ed in patients with allergic rhinitis. Interestingly, patients without symptoms an the day of the test also showed a clear-cut increase in n asal NO production, which could reflect a permanent inflammation of th e sinus mucosa.