| Abstract: | Sphingomyelin synthesis was studied in slices of rat heart by using Me-14C]choline, 1,2-14C]ethanolamine, S-adenosyl-L-14C]methionine and 32P]Pi as as precursors. In the presence of both Me-14C]choline and 32P]Pi the ratio of the specific radioactivities of 14C and 32P in phosphatidylcholine was greater than in sphingomyelin at all the times studied. This suggested that synthesis of phosphatidylcholine and sphingomyelin de novo did not involve the utilization of a common pool of cytidine diphosphate choline. In addition, studies with 1,2-14C]ethanolamine and S-adenosyl-L-14C]methionine indicated that a quantitatively significant pool of choline, derived from these precursors, was selectively utilized for sphingomyelin formation. This pool was not represented by phosphatidylcholine formed by methylation of phosphatidylethanolamine or by other pathways. |
