| Summary: | When excised rat diaphragms are incubated with palmitate-l-C14, radioactivity is found in triglyceride, diglyceride, and monoglyceride. The specific activity of diglyceride exceeds that of triglyceride after the various time periods studied. With increasing incubation time, the specific activity of triglyceride gradually approaches that of diglyceride. When diaphragm is incubated with labeled palmitate and then transferred to a second medium containing unlabeled palmitate, there is a marked decrease in the specific activity of the diglyceride fraction. There is formation of labeled triglyceride when a cell-free, particulate preparation of diaphragm is incubated with labeled dipalmitin and palmitoyl-CoA. After very short incubation periods with labeled palmitate, the specific activity of the total neutral lipid is significantly higher than that of the total phospholipid. In addition, the values obtained in these experiments were compared with the values obtained in a second study of individual phosphatides of diaphragm. In all instances, the specific activity of the diglyceride exceeded that of the glycerol phosphatides that were isolated. The data are consonant with the hypothesis that diglyceride is a precursor of triglyceride and glycerol phosphatides.
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