LECITHIN SYNTHESIS IN THE FETAL AND NEONATAL PRIMATE LUNG AS MEASURED in vitro

Abstract

Two pathways are present in fetal primate lung for de novo synthesis of lecithin: the choline incorporation route (I) and phosphatidyl ethanolamine (PE) methylation (II). Based on fatty acid analyses it has been proposed (Pediat. Res. 6:81, 1972) that the latter pathway is predominant in the human fetus until late gestation. Accordingly, lung slices from Rhesus monkeys were incubated with isotopic precursors including either ¹⁴C-choline (I), ¹⁴C-methionine (II), or ¹⁴C-ethanolamine (II) and incorporation of isotope into lecithin was determined. Measurement of precursor uptake was also performed, and the phospholipid synthesis rates were adjusted for isotope transport.

The major pathway in all animals examined is the choline incorporation route. Whereas II shows a relatively constant, low rate throughout gestation (term 164 days), I increases at 150 days gestation (p<.05) and then decreases in the neonate.

It is concluded that pathway I is predominant and accounts for increased lecithin synthesis in the mature fetus as well as for the surge in amniotic fluid lecithin/sphingomyelin ratio.

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