Abstract
ABSTRACT. Pohlandt, F. (Department of Paediatrics, Section of Neonatology, University Hospital, Ulm, Federal Republic Germany). Cystine: a semi‐essential amino acid in the newborn infant. Acta Paediatr Scand63: 801, 1974.—The enzyme activities of the transsulfuration pathway (Cystine biosynthesis) are low or not measurable in the livers of human fetuses, premature and full‐term newborns. Cystine thus may be an essential amino acid in newborn infants. To test this suggestion, we studied the plasma amino acid concentrations in 20 premature and 7 full‐term infants treated for prematurity and/or respiratory distress syndrome by ion exchange columnchromatography. The infants received infusions of a 5% glucose‐electrolyte‐solution during the first two days of life. In premature newborns the plasma cystine concentrations markedly decreased within the first 12 hours of life (median <5 μmol/l) and remained low tlfereafter. In full‐term infants the plasma cystine concentrations decreased similarly. To rule out the possibility that these low plasma cystine concentrations were the result of a reduced cystine biosynthesis due to a lack of methionine, a substrate of transsulfuration pathway, we studied premature on infusion of a mixture of synthetic l‐amino acids free from cystine. Despite elevated plasma methionine concentrations (median 113.4 μnol/l) the plasma cystine concentrations remained very low. Cystine, therefore, can be considered a semi‐essential amino acid in the newborn infant and should be supplied to newborns receiving balanced parenteral nutrition.
Published Version
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