Lipid Synthesis from [U-14C] Glucose in Preimplantation Mouse Embryos in Culture

Mouse embryos were cultured from the 2-cell to the morula stage in a medium containing [U-14C] glucose. Total lipid was extracted and the distribution of radioactivity was determined in the neutral lipid, phospholipid and glycolipid fractions eluted from a silicic acid column and in the individual lipids separated from these fractions by thin layer chromatography. The partitioning of radioactivity between a chloroform and aqueous phase after alkaline methanolysis of the fractions from silicic acid column chromatography was also studied. Of the total lipid radioactivity, almost 80% was recovered in the neutral lipid fraction. Most of the neutral lipid label was present in the triacylglycerols. The remaining 20% of the total radioactivity was distributed between the phospholipid and glycolipid fractions. Phosphatidylcholine accounted for 68% of the phospholipid radioactivity. The remainder of the phospholipid associated radioactivity was recovered in phosphatidylethanolamine and in phosphatidylinositol and/or phosphatidylserine. The distribution of label after alkaline methanolysis of the neutral lipid and phosphobipid fractions showed that most of the radioactivity was present in the glycerol backbones and not in the fatty acids of these compounds. The major glycolipids synthesized were cerebrosides, however, evidence was obtained for the presence of a glyceroglycolipid.