Background: The present study was aimed to obtain information on the interaction kinetics of L-tryptophan (L-Trp) with plasma albumin from normal, intrauterine growth-restricted (IUGR) and nutritionally recovered (NR) newborn infants.
Methods: A case study cohort was planned in 37 newborns during the first 3 months of life. At birth two groups were formed. The first group included 20 newborns with IUGR. The control group (C) included 17 appropriate for gestational age newborns. At 30 days of age, 9 infants of the IUGR group showed a return to normal of the anthropometric parameters, these infants formed the NR group. Free, bound and total L-Trp were measured. To assess binding kinetics albumin was freed of fatty acids and tested in mole to mole samples from IUGR, NR and control babies.
Results: Plasma free L-Trp was increased, K(d) (dissociation constant) elevated and B(max )(maximal binding)decreased in IUGR patients up to postnatal day 90. These changes remained even after nutritional recovery.
Conclusions: Abnormal kinetics of L-Trp binding to albumin explains the increased availability of this precursor amino acid in the plasma of IUGR infants. This finding corroborates previous results in IUGR rats and newborn babies, indicating enhanced potential for brain serotonergic synthesis.