Changes in exhaled nitric oxide after ingestion of L‐arginine in children: A pilot study

RATIONALE: Exhaled nitric oxide (FE(NO)) may be a useful biomarker for asthma and is derived from enzymatic activity on the amino acid L-arginine. The aim of the present pilot study was to study the effect of L-arginine ingestion on FE(NO) and also NO production in the proximal and distal airways. METHODS: Asthmatic and control children were enrolled and phenotyped by skin prick reactivity and spirometry. FE(NO) was measured before and after ingestion of 0.2 g/kg L-arginine. Proximal and distal NO production (J'awNO and CANO) were derived using the method of Tsoukias. RESULTS: Twenty children were recruited, 11 steroid-treated asthmatics, 1 steroid-naïve asthmatic, and 8 healthy controls. The median baseline FE(NO) before L-arginine administration was 31 ppb (interquartile range, IQR, 15, 61). At baseline, the median J'awNO was 1000 nl/sec (IQR 650, 2880) and the median CANO was 2.3 ppb (IQR 1.8, 4.5). FE(NO) rose by an average of 5.5 ppb [95% CI 3.5, 7.5] (P < 0.001) 60 min after ingestion of L-arginine and 1.5 ppb [95% CI -0.9, 4.0] (P = 0.188) after 120 min. One hour after L-arginine ingestion, J'awNO did not change but CANO rose by an average of 2.6 ppb [95% CI 0.5, 4.7], P = 0.020. CONCLUSION: The rise in FE(NO) after dietary exposure to L-arginine is modest, transient, and of little or no clinical significance.