Objective Plasma arginine concentrations are decreased in premature infants with necrotising enterocolitis (NEC). Recently, we described a correlation between a functional polymorphism (the substitution of asparagine for threonine at position 1405 (T1405N)) in carbamoyl-phosphate synthetase (CPS), which limits arginine concentrations in term infants, and the presence of NEC in preterm infants. We hypothesised that this functional polymorphism in the CPS-1 gene would affect the basal arginine concentrations (6–12 h after birth) in preterm infants.
Methods Plasma concentrations of amino acids and genotypes of the carbamoyl-phosphate synthetase variants were determined in 39 preterm infants (<30 weeks gestation and <1500 g birth weight). Samples were taken between 6 and 12 h after birth.
Results The distribution of the genotypes (CC : CA : AA = 51.3% : 33.3% : 15.4%) was not significantly different when compared with the general population. Infants who were homozygous (CC) for the C-encoded Thr1405 enzyme had no different mean plasma concentrations of arginine compared with infants with the AA genotype and hence the Asn1405 enzyme (78.5, SD 49.2 vs 48.0, SD 16.1 μmol/l, p = 0.18).
Conclusions In this small group of preterm infants we did not find an association between the T1405N CPS-1 polymorphism and lower basal arginine concentrations. However, under conditions of environmental stress (ie, NEC) the infants with the CC genotype might have a disadvantage in terms of urea-cycle function and interrelated metabolic processes.