title: Surfactant-associated protein B kinetics in vivo in newborn infants by stable isotopes.
abstract: Surfactant-associated protein B (SP-B) is critical to the biophysical function of pulmonary surfactant. No information is available on SP-B synthesis and kinetics in humans. We administered a 24-h i.v. infusion of 13C-valine as metabolic precursor of SP-B to six newborn infants (weight 3.5+/-0.5 kg; age 12 d, range 1-43 d). Three of the study infants also received i.v. 2H-palmitate to label surfactant disaturated phosphatidylcholine (DSPC). SP-B and DSPC were isolated from tracheal aspirates, and their respective 13C and 2H enrichments were measured by gas chromatography-mass spectrometry. SP-B kinetics was measured successfully in all six infants. SP-B median (range) fractional synthesis rate was 30% per day (20-78% per day), secretion time was 4.5 h (1-9 h), time to peak was 24 h (12-36 h), and half-life was 21 h (8-35 h). The ascending part of the SP-B kinetic curve was similar to the DSPC curve, suggesting similar secretion pathways. SP-B half-life seemed to be shorter than DSPC half-life. These results agree with existing animal data. We conclude that the measurement of SP-B kinetics is feasible in vivo in humans by stable isotope technology.
authors.affiliation: Department of Pediatrics, University of Padova, Padova, and Pharmacy, Salesi Children Hospital, Ancona, Italy. cogo@pediatria.unipd.it
authors.forename: Paola
authors.initials: P
authors.lastname: Cogo
authors.forename: Aldo
authors.initials: A
authors.lastname: Baritussio
authors.forename: Federica
authors.initials: F
authors.lastname: Rosso
authors.forename: Antonina
authors.initials: A
authors.lastname: Gucciardi
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Moretti
authors.forename: Tamara
authors.initials: T
authors.lastname: Badon
authors.forename: Elena
authors.initials: E
authors.lastname: Duner
authors.forename: Luc
authors.initials: L
authors.lastname: Zimmernann
authors.forename: Virgilio P
authors.initials: VP
authors.lastname: Carnielli
mesh_terms: D002247:Carbon Isotopes / Q000378:metabolism; D003903:Deuterium / Q000378:metabolism; D006207:Half-Life; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D010168:Palmitates / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism; D037701:Pulmonary Surfactant-Associated Protein B / Q000096:biosynthesis / Q000378:metabolism*; D014633:Valine / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D010168:Palmitates; D010713:Phosphatidylcholines; D037701:Pulmonary Surfactant-Associated Protein B; D003903:Deuterium; D014633:Valine