Clearance of intra-amniotic lung surfactant: uptake and utilization by the fetal rabbit lung.
To investigate the metabolism of intra-amniotic surfactant, surfactant containing double-labeled dipalmitoylphosphatidylcholine (DPPC) was injected in amniotic fluid on days 23-27 of gestation. Within 44 h, DPPC was distributed to the gastrointestinal tract (45.9%), fetal membranes and placenta (8.2%), fetal lung (6.6%), and liver (1.9%). DPPC uptake was higher in the upper than in the lower lung lobes. The mixture of phosphatidylglycerol and DPPC increased the uptake of DPPC that was not saturable (range 15-60 mg phospholipid). There was no detectable metabolism of DPPC taken up by the fetal lung. Surfactant protein A, originating from intra-amniotic heterplogous surfactant, was detected immunohistochemically in alveolar epithelium. Intra-amniotic surfactants did not affect the expression of surfactant protein mRNAs. Intra-amniotic surfactant (1,500-2,000 mg/kg on day 25.3) improved lung compliance of ventilated 27.0-day premature rabbits less than intratracheal surfactant at birth (75-100 mg/kg). Reutilization by the alveolar epithelium of surfactant secreted to future airspaces, airways, and amniotic fluid may be a mechanism that increases intracellular surfactant pool before birth.
Hallman
M
M
Department of Pediatrics, University of California, Irvine 92697, USA.
Lappalainen
U
U
Bry
K
K
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000493:pharmacokinetics; D000653:Amniotic Fluid / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D002250:Carbon Radioisotopes; D005260:Female; D005333:Fetus; D005865:Gestational Age; D008168:Lung / Q000196:embryology* / Q000502:physiology; D008657:Metabolic Clearance Rate; D011247:Pregnancy; D011510:Proteolipids / Q000096:biosynthesis; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000096:biosynthesis* / Q000493:pharmacokinetics*; D012333:RNA, Messenger / Q000096:biosynthesis; D011817:Rabbits; D011865:Radioisotope Dilution Technique; D014018:Tissue Distribution; D014158:Transcription, Genetic; D014316:Tritium
D002250:Carbon Radioisotopes; D011510:Proteolipids; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D012333:RNA, Messenger; D014316:Tritium; D015060:1,2-Dipalmitoylphosphatidylcholine