Comparison of cadmium and enzyme-catalyzed nitrate reduction for determination of NO2-/NO3- in breath condensate

Background: Analysis of NO2-/NO3- in expired breath condensate (EBC) has been proposed as a marker of inflammation in various lung diseases. Methods: NO2- and total NO3-/NO2- concentrations were determined in EBC collected from healthy and asthmatic subjects. The NO3- was first reduced to NO2-, and total NO2- was detected by colorimetric Griess reaction. Two methods of NO3- reduction were compared. To reduce NO3-, cadmium (600 mul EBC-macromethod) and enzyme-NADPH-nitrate reductase (60 mul EBC-micromethod) were used. Results: Macromethod: Mean NO2- concentrations in EBC were 1.64+/-0.24 mumol/l in healthy subjects and 0.42+/-0.17 mumol/l in asthmatic patients. Mean total NO2-/NO3- levels were 3.64+/-0.43 mumol/l in healthy subjects and 3.27+/-0.34 mumol/l in asthmatic. Micromethod: NO2- level: 1.69+/-0.23 mumol/l in healthy subjects and 0.53+/-0.21 mumol/l in asthmatics. Total No-2(-)/NO3- levels: 3.56+/-0.37 mumol/l in healthy subjects and 3.57+/-1.17 mumol/l in for enzymatic and almost 88% for cadmium reduction. There was no correlation between total NO2-/NO3- levels determined by macro- and micromethod. Conclusions: We recommend enzymatic reduction as a better method for NO3- determination in EBC. (C) 2003 Elsevier B.V. All rights reserved.