METABOLITES OF NITRIC-OXIDE IN THE LOWER RESPIRATORY-TRACT OF CHILDREN

Nitric oxide (NO) is produced in the upper and lower respiratory tract and can be detected in exhaled air of both healthy individuals and su bjects with pulmonary diseases. Recent studies have shown that exhaled NO is mainly derived from the upper airways. There is, however, evide nce that in aqueous solutions NO is rapidly converted to distinct oxid es of nitrogen. We therefore studied the stable NO metabolites nitrate and nitrite in broncho-alveolar lavage (BAL) fluid and serum as indic ators of NO formation in the lower respiratory tract. The study popula tion consisted of 31 healthy children undergoing elective surgery for nonpulmonary illnesses and 13 immunosuppressed children with pneumonia . Nitrate and nitrite were determined photometrically. Nitrate was fou nd in BAL fluid of all children. In children with pneumonia, nitrate c oncentrations in BAL fluid were significantly higher than in healthy c hildren. A significant correlation was observed between nitrate in BAL fluid and serum of immuno-suppressed children with pneumonia. Nitrite was not detected in any of the BAL fluid or serum samples. Conclusion s Our results suggest that in the lower airways significant amounts of NO are metabolised to nitrate. Studies on NO in pulmonary diseases sh ould therefore include determination of nitrate in lower airway fluids .