Fibronectin turnover in the premature neonate measured with [15N]glycine.
Fibronectin is a large-molecular-weight glycoprotein present on most cell surfaces and in plasma. Plasma fibronectin concentrations in neonates are lower than those in adults and a direct relationship exists between plasma concentration and gestational age. We determined the half-life and fractional synthetic rate (FSR) of plasma fibronectin in the premature infant. Infants and adults received a loading dose of [15N]glycine followed by a constant infusion [15N]glycine incorporation into plasma fibronectin and urine hippurate was determined by gas chromatography-mass spectrometry. The plasma fibronectin FSR in the preterm neonates was 15.5 +/- 9.9%/d(means +/- SD) and the half-life was 5.55 +/- 2.25 d. Birth weight correlated inversely with plasma fibronectin half-life. In the adults the plasma fibronectin FSR ranged from 20 to 87%/d and half-life ranged between 0.79 and 3.47 d. These data suggest that decreased plasma fibronectin levels in preterm infants are due to reduced FSRs rather than to greater turnover of a relatively small plasma pool.
Polin
R A
RA
Division of Neonatology, Children's Hospital of Philadelphia, PA 19104.
Yoder
M C
MC
Douglas
S D
SD
McNelis
W
W
Nissim
I
I
Yudkoff
M
M
D000328:Adult; D005353:Fibronectins / Q000493:pharmacokinetics*; D005865:Gestational Age; D005998:Glycine / Q000493:pharmacokinetics*; D006626:Hippurates / Q000652:urine; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D009587:Nitrogen Isotopes
D005353:Fibronectins; D006626:Hippurates; D009587:Nitrogen Isotopes; C030514:hippuric acid; D005998:Glycine