title: Surfactant protein C metabolism in human infants and adult patients by stable isotope tracer and mass spectrometry.
abstract: Surfactant protein C (SP-C) is deemed as the surfactant protein most specifically expressed in type II alveolar epithelial cells and plays an important role in surfactant function. SP-C turnover in humans and its meaning in the clinical context have never been approached. In this study, we used mass spectrometry to investigate SP-C turnover in humans. We studied four infants and eight adults requiring mechanical ventilation. All patients had no lung disease. Patients received a 24-h continuous infusion of (13)C-leucine as precursor of SP-C, and serial tracheal aspirates and plasma samples were obtained every 6 h till 48 h. SP-C was isolated from tracheal aspirates by sorbent-phase chromatography. (13)C-leucine SP-C enrichment could be successfully measured in three infant and in four adult samples by using mass spectrometry coupled with a gas chromatographer. Median SP-C fractional synthesis rate, secretion time, and peak time were 15.7 (14.1-27.5)%/day, 6.0 (4.7-11.5) h, and 24 (20-27) h. In conclusion, this study shows that it is feasible to accurately determine SP-C turnover in humans by stable isotopes.
authors.affiliation: Women's and Children's Health Department, University of Padova, 35128, Padova, Italy, manuela.simonato@unipd.it.
authors.forename: Manuela
authors.initials: M
authors.lastname: Simonato
authors.forename: Aldo
authors.initials: A
authors.lastname: Baritussio
authors.forename: Barbara
authors.initials: B
authors.lastname: Pioselli
authors.forename: Carlo
authors.initials: C
authors.lastname: Ori
authors.forename: Silvia
authors.initials: S
authors.lastname: Catinella
authors.forename: Virgilio P
authors.initials: VP
authors.lastname: Carnielli
authors.forename: Paola E
authors.initials: PE
authors.lastname: Cogo
mesh_terms: D000328:Adult; D000368:Aged; D002247:Carbon Isotopes / Q000737:chemistry; D005260:Female; D006801:Humans; D007223:Infant; D007553:Isotope Labeling / Q000379:methods*; D007700:Kinetics; D008297:Male; D013058:Mass Spectrometry / Q000379:methods*; D008875:Middle Aged; D037721:Pulmonary Surfactant-Associated Protein C / Q000097:blood / Q000737:chemistry* / Q000378:metabolism; D014132:Trachea / Q000737:chemistry / Q000378:metabolism; D055815:Young Adult
chemical_list: D002247:Carbon Isotopes; D037721:Pulmonary Surfactant-Associated Protein C; C489679:SFTPC protein, human