Changes in exhaled nitric oxide after ingestion of L-arginine in children: a pilot study

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.

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.

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.

The rise in FE(NO) after dietary exposure to L-arginine is modest, transient, and of little or no clinical significance.