FIGURE 4.

Incorporation of stable isotope–labeled choline into plasma PC in preterm infants. (A) The fractional enrichment of methyl-D₉-PC (solid line, mean ± SEM) synthesized by the CDP-choline pathway and of methyl-D₃-PC synthesized by the PEMT pathway (dashed line, mean with SEM smaller than symbol). There were 31 infants at t = 0, and numbers of infants at each time point are indicated on the figure. (B) The same results as in panel A after normalization to the initial concentration value using the variation in PC concentration with time detailed in Figure 2B. CDP-choline, cytidine diphosphocholine; PC, phosphatidylcholine; PEMT, phosphatidylethanolamine N-methyltransferase.