To determine whether l -arginine concentrations (the substrate for nitric oxide synthesis) are lower in premature infants in whom necrotizing enterocolitis (NEC) develops than in unaffected infants.

We measured arginine and nutritional intake, plasma arginine, glutamine, total amino acids, and ammonia concentrations in 53 premature infants (mean gestational age ± SD: 27 ± 1.7 weeks) at risk of NEC. Measurements were done on days 3, 7, 14 and 21 and just before treatment in infants with NEC.

Necrotizing enterocolitis developed in 11 infants between postnatal days 1 and 26. On day 3, plasma arginine concentrations were decreased compared with normal published values (mean ± SE, 41 μmol/L ± 4). Arginine concentrations increased with day of life of measurement ( p < 0.001) and arginine intake ( p < 0.001). Plasma arginine concentrations were significantly lower at the time of diagnosis in infants with NEC compared with control subjects, even after adjusting for arginine intake and day of life ( p = 0.032). Plasma glutamine and total amino acid concentrations were not significantly different in infants with NEC compared with control subjects. Plasma ammonia concentrations were elevated on day 3 (mean ± SE, 72 ± 3.3 μmol/L) and decreased with postnatal age ( p < 0.001) and increasing plasma arginine concentrations ( p < 0.001).

Plasma arginine concentrations are decreased at the time of diagnosis in premature infants with NEC. The potential benefit of arginine supplementation in the prevention of the disease deserves evaluation. (J Pediatr 1997;131:226-32)