Characterization of airway nitric oxide in allergic rhinitis: the effect of intranasal administration of L-NAME.
BACKGROUND
Several studies have attempted to assess nasal nitric oxide (NO) levels in allergic rhinitis (AR). However, there seem to be differences in the results obtained. We therefore wanted to investigate this further by studying airway NO in AR and controls at several modalities, and also the effect of intranasal administration of the nitric oxide synthase (NOS) inhibitor NG-nitro-L-arginine-methyl ester.HCl (L-NAME).


METHODS
Airway NO was determined through repeated measurements at three flow rates of air (0.5, 3, and 9 l/min), using a single-breath method and a method of nasal aspiration, in 18 patients with birch pollen AR during season and in 18 controls.


RESULTS
Patients with AR were characterized by no difference in nasal but higher orally exhaled NO and a larger interindividual spread in nasal and orally exhaled NO compared to controls. We also found a greater reduction in nasal NO after L-NAME in patients compared to controls.


CONCLUSIONS
These results indicate that several factors determine the levels of nasal NO in rhinitis. NO production in the nasal mucosa of patients with AR may be upregulated. On the other hand, this increase could be counteracted by swelling of the mucosa and secretions resulting in impaired NO diffusion from, for example, the paranasal sinuses, where particularly high levels of NO have been found. Also, the high background levels of NO from constitutive sources in the nose may blunt smaller increases in mucosal NO output.


CONCLUSIONS
It seems that the methods for measurement of nasal NO need to be improved and standardized before we can consider to use this test in monitoring inflammation in AR.
Palm
J P
JP
Department of Physiology and Pharmacology, Karolinska Institutet, S-171 77 Stockholm, Sweden.
Alving
K
K
Lundberg
J O
JO
D000281:Administration, Intranasal; D000328:Adult; D001944:Breath Tests; D016022:Case-Control Studies; D004791:Enzyme Inhibitors / Q000008:administration & dosage*; D045853:Exhalation; D006801:Humans; D006967:Hypersensitivity / Q000150:complications*; D008875:Middle Aged; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage*; D009296:Nasal Cavity / Q000378:metabolism*; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011058:Pollen / Q000276:immunology; D012220:Rhinitis / Q000209:etiology* / Q000378:metabolism*; D014197:Trees / Q000276:immunology
D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D019331:NG-Nitroarginine Methyl Ester