Elevated plasma peptide YY in human neonates and infants.

Plasma concentrations of peptide YY (PYY) were measured in cord blood and at 6, 12, and 18 days of postnatal life in 24 healthy preterm neonates, from cord blood of eight full-term neonates, and from peripheral blood of 13 infants 9 months old. Concentrations were high in cord blood (73 +/- 9 pmol/liter versus adult fasting 10.4 +/- 1.3, p less than 0.001) and rose postnatally in the premature infants to 399 +/- 48 pmol/liter at 6 days, 489 +/- 42 at 12 days, and fell to 414 +/- 43 at 18 days. Plasma PYY concentrations were much lower in infants 9 months old (32 +/- 3 pmol/liter), suggesting that the postnatal surge of plasma PYY is a feature of early adaptation to extrauterine life. Gel permeation chromatograms revealed that the major circulating form of PYY in the neonate eluted in a position identical to that of the pure 36 amino acid peptide. There was, however, evidence of two larger molecular forms that may be precursor molecules. Because PYY is a peptide that exhibits potent effects on gastrointestinal secretion and motility in humans, these observations suggest that this candidate gut hormone may be important in the adaptation to enteral nutrition in the neonate.