Studies on the Phospholipid Metabolism in Choline-Deficient Guinea Pigs

1. Lecithin syntheses from four radioactive precursors in liver slices were compared between the choline-deficient and the choline-supplemented (control) guinea pigs.2. In the choline-deficient group, more 32PO4 was incorporated into lecithin than into phosphatidylethanolamine, whereas this relationship was reversed in the control group.3. Incorporation of choline-14CH3 into lecithin in the choline-deficient group was twice as great as that in the control.4. No difference was observed between the two groups in the incorporation of ethanolamine-14C into phosphatidylethanolamine. However, a larger part of the incorporated radioactivity was found in lecithin in the choline-deficient group than in the control.5. Incorporation of labeled methyl group from L-methionine-C3H3 was also doubled in the choline-deficient group as compared with the control.6. As the activity of methionine activating enzyme was almost at the same level in the two groups, the higher activity of phosphatidylmethyltransferase system was expected to be responsible for the higher phospholipid methylating activity in the choline-deficient group.7. Incorporation of labeled methyl group into phospholipids was augmented nearly twice by preincubating the slices with N-methylethanolamine or N, N-dimethylethanolamine prior to the addition of L-methionine-C3H3.