title: Endogenous surfactant turnover in preterm infants measured with stable isotopes.
abstract: We studied surfactant synthesis and turnover in vivo in preterm infants using the stable isotope [U-13C]glucose, as a precursor for the synthesis of palmitic acid in surfactant phosphatidylcholine (PC). Six preterm infants (birth weight, 916 +/- 244 g; gestational age, 27.7 +/- 1.7 wk) received a 24-h [U-13C]glucose infusion on the first day of life. The 13C-enrichment of palmitic acid in surfactant PC, obtained from tracheal aspirates, was measured by gas chromatography-combustion interface-isotope ratio mass spectrometry. We observed a significant incorporation of carbon-13 from glucose into surfactant PC palmitate. PC palmitate became enriched after 19.4 +/- 2.3 (16.5 to 22.3) h and reached maximum enrichment at 70 +/- 18 (48 to 96) h after the start of the label infusion. The fractional synthesis rate (FSR) of surfactant PC palmitate from glucose was 2.7 +/- 1.3%/d. We calculated the absolute production rate of surfactant PC to be 4.2 mg/kg/d, and the half-life to be 113 +/- 25 (87 to 144) h. Data on endogenous surfactant production and turnover were obtained for the first time in human infants with the use of stable isotopes. This novel and safe method could be applied to address many important issues concerning surfactant metabolism in preterm infants, children, and adults.
authors.affiliation: Department of Pediatrics, Sophia Children's Hospital, Erasmus University Rotterdam, The Netherlands.
authors.forename: J E
authors.initials: JE
authors.lastname: Bunt
authors.forename: L J
authors.initials: LJ
authors.lastname: Zimmermann
authors.forename: J L
authors.initials: JL
authors.lastname: Wattimena
authors.forename: R H
authors.initials: RH
authors.lastname: van Beek
authors.forename: P J
authors.initials: PJ
authors.lastname: Sauer
authors.forename: V P
authors.initials: VP
authors.lastname: Carnielli
mesh_terms: D000328:Adult; D001724:Birth Weight; D001786:Blood Glucose / Q000032:analysis; D002247:Carbon Isotopes; D002648:Child; D002852:Chromatography, Ion Exchange; D002855:Chromatography, Thin Layer; D004791:Enzyme Inhibitors / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D005865:Gestational Age; D005947:Glucose / Q000378:metabolism; D006207:Half-Life; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000378:metabolism*; D007262:Infusions, Intravenous; D019308:Palmitic Acid / Q000378:metabolism; D010713:Phosphatidylcholines / Q000096:biosynthesis; D011663:Pulmonary Surfactants / Q000096:biosynthesis / Q000378:metabolism*; D012449:Safety; D013396:Suction; D013997:Time Factors; D014132:Trachea
chemical_list: D001786:Blood Glucose; D002247:Carbon Isotopes; D004791:Enzyme Inhibitors; D010713:Phosphatidylcholines; D011663:Pulmonary Surfactants; D019308:Palmitic Acid; D005947:Glucose