Elsevier

Nitric Oxide

Volume 8, Issue 1, February 2003, Pages 26-30
Nitric Oxide

Nitrate in exhaled breath condensate of patients with different airway diseases

https://doi.org/10.1016/S1089-8603(02)00128-3Get rights and content

Abstract

There is an increasing interest in the measurement of nitric oxide (NOradical dot) in the airways. NOradical dot is a free radical that reacts rapidly with reactive oxygen species in aqueous solution to form peroxynitrite which can then break down to nitrite (NO2) and nitrate (NO3). NO3 is considered a stable oxidative end product of NOradical dot metabolism. The aim of this study was to assay NO3 in exhaled breath condensate (EBC) of normal nonsmoking and smoking subjects, asthmatics, patients with obstructive pulmonary disease (COPD), and patients with community-acquired pneumonia (CAP). EBC was collected using a glass condenser and samples were assayed for NO3 by ion chromatography followed by conductivity measurement. NO3 was detectable in EBC of all subjects. NO3 was elevated in smokers [median (range)] [62.5 (9.6–158.0) μM] and in asthmatics [68.0 (25.8–194.6) μM] compared to controls [9.6 (2.6–119.4) μM; p=0.003 and p=0.006, respectively], whereas NO3 was not elevated in COPD patients [24.1 (1.9–337.0) μM]. The concentration of NO3 in patients with CAP [243.4 (26.1–584.5) μM] was higher than that in controls (p=0.002) and NO3 values decreased after treatment and recovery from illness [40.0 (4.1–167.0) μM, p=0.009]. This study shows that NO3 is detectable in EBC of healthy subjects and it varies in patients with inflammatory airway diseases.

Section snippets

Study design

Preliminarily, we measured NO3 in EBC of healthy volunteers both with the chromatographic method and with the Griess method. The analysis of the degree of concordance (Bland and Altman test [13]) indicated the agreement of the two methods (Fig. 1).

In a preliminary study, we evaluated the reproducibility of the chromatographic method for the measurement of NO3 concentration in EBC. The difference in EBC NO3 concentrations measured during two successive collections at 2-h intervals (intraday

Results

All the subjects performed the EBC procedure without discomfort. NO3 levels in EBC measured with the chromatographic method were detectable in all subjects.

NO3 values were higher in smokers [median (range) 62.5 (9.6–158.0) μM] than in controls [9.6 (2.6–119.4) μM; p=0.003] (Fig. 3). NO3 levels positively correlated with the smoking history expressed as cigarettes per day (r=0.5, p=0.02). No correlation was observed between NO3 levels and smoking history expressed as pack–years and as exhaled

Discussion

The results of this study show high NO3 levels in EBC of asymptomatic smokers, asthmatics, and patients with CAP, but not in COPD patients in comparison to healthy nonsmoking subjects.

In this study NO3 concentrations in EBC were assayed using the chromatographic method. The chromatographic method for the measurement of NO3 has the advantages of minimal sample preparation and rapid analysis time (3 min per sample); therefore it is particularly suitable for assaying several samples at the same

Acknowledgements

The authors are grateful to Professor Bacciottini Franco and Dr. Friggeri Marco for their skillful assistance in the biochemical assays. We also thank Professor Paolo Montuschi for providing EBC samples of asthmatic patients.

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