Phospholipid metabolism in the developing liver : I. The biosynthesis of choline glycerophosphatides by liver slices from fetal, newborn and adult rats

Abstract

1. 1. The biosynthesis of choline glycerophosphatides was evaluated in fetal, neonatal and adult female rat liver. The two main pathways were assessed by studying the rates of incorporation of [Me-14C]choline and [Me-14C]methionine by liver slices.2. 2. Over 96% of the lipid radioactivity from [Me-14C] choline was located in choline glycerophosphatides. In adult liver slices 93% of the total lipid radioactivity from [Me-14C]methionine was located in choline glycerophosphatides. An appreciable amount of radioactivity from [Me-14C]methionine was incorporated into fatty acids by fetal liver slices.3. 3. Liver slices from fetal rats incorporated the same amount of [Me-14C]choline into lecithin as did adult liver slices except for a drop 2 days before birth. Liver slices from 3-day-old neonatal rats incorporated about twice as much [Me-14C]choline as the adult liver slices.4. 4. Liver slices from fetal and young rats incorporated about 8-10 times more [Me-14C]choline into phosphoryl choline than did liver slices from adults. Adult levels were reached at 10 days after birth.5. 5. The incorporation of radioactivity from [Me-14C]methionine into lecithin by fetal liver slices was much lower than that by adult liver slices and increased to twice adult levels by 10-12 days after birth. Adult levels were reached by 25 days after birth.6. 6. Studies with [1,2-14C2, Me-14H]choline indicated that the choline was incorporated intact and that little, if any, of the methyl groups of choline were used for the methylation of phosphatidyl ethanolamine.7. 7. The mechanism of choline incorporation into lecithin is discussed.