Exhaled NH3 and excreted NH4+ in children in unpolluted or urban environments

Exhaled ammonia (NH(3)ex) was measured by chemiluminescence in a group of healthy children (n = 20) and in two groups of asthmatic children, one (Group 1) residing in a National Park in the mountains (n = 68) and other (Group 2) in an urban area (n = 52). We also determined urinary ammonia, nitrates, urea, sodium and potassium normalized to osmolarity. Unlike exhaled nitric oxide (NOex), NH(3)ex was not specific to asthma as the children in Group 2 and the controls exhaled more ammonia that did the children in Group 1 (14.3 +/- 10.2 and 14.8 +/- 10.3 vs. 5.6 +/- 4.7 ppb; P <.001, respectively). In the urban environment, all children, including the healthy controls, excreted more ammonia (P <.001) and potassium (P <.001) but less urea (P <.02) than did the children residing in the National Park. These manifestations of moderate metabolic acidosis would favor excretion of ammonia at the expense of urea. In the children residing in the National Park, positive correlations were observed between NH(3)ex and urinary ammonia, and nitrates, age and morphological parameters. The relationship with the morphological parameters is a reflection of the normal physiological formation of NH(3)ex. In the children residing in the urban area, the other endogenous source of NH(3)ex was attributed to a slight disturbance in acid-base balance. In conclusion, the measurement of NH(3)ex appeared of limited interest, although the higher urinary urea/NH4+ ratio in Group 1 (P<.0001), especially in the treated children, appeared to be linked to the lack of atmospheric pollutants in the National Park. Further experimentation is in progress to confirm these findings. (C) 2002 Elsevier Science Ltd. All rights reserved.