Surfactant protein B amount and kinetics in newborn infants: an optimized procedure

J Mass Spectrom. 2012 Nov;47(11):1415-9. doi: 10.1002/jms.3065.

Abstract

Surfactant protein B (SP-B) plays a key role in surfactant homeostasis affecting its biophysical properties and physiological function. Recently, a method to measure SP-B amount and kinetics from tracheal aspirates (TAs) became available. The main objective of this study was to improve the critical steps of the procedure to obtain a better SP-B sensitivity. We administered a 24 h continuous infusion of 1 mg/kg/h of 1(13)C-leucine to ten newborn infants. SP-B was isolated from serial TAs and its fractional synthesis rate, secretion time, peak time and half life were derived from (13)C enrichment curves obtained by gas chromatography mass spectrometry. SP-B amount in TAs was also assessed. During the extraction step, acidification and organic solvent ratio optimization doubled the recovery of SP-B from TAs, so did the elongation of the propylation time (from 20 min to 1 h) with enhanced leucine derivatization yield. Measurement of (13)C leucine enrichments, and therefore all SP-B kinetics parameters, were successfully calculated in all TAs samples due to the increase of SP-B yield. SP-B amount was 0.29 (0.16-0.41) % of total phospholipids with a minimum value of 0.08% belonging to one of the respiratory distress syndrome (RDS) patients. In conclusion, this new procedure enables accurate determination of SP-B kinetics even in the presence of low protein amount like in preterm RDS patients.

MeSH terms

  • Bodily Secretions / chemistry
  • Bodily Secretions / metabolism
  • Carbon Isotopes
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Humans
  • Infant
  • Infant, Newborn / metabolism*
  • Kinetics
  • Leucine / administration & dosage
  • Leucine / pharmacokinetics
  • Male
  • Mass Spectrometry / methods
  • Phospholipids / analysis
  • Phospholipids / metabolism
  • Protein Precursors / analysis*
  • Protein Precursors / metabolism
  • Proteolipids / analysis*
  • Proteolipids / metabolism
  • Trachea / metabolism

Substances

  • Carbon Isotopes
  • Phospholipids
  • Protein Precursors
  • Proteolipids
  • surfactant protein B propeptide
  • Leucine