Lipid metabolism in bone and bone cells II. The in vitro incorporation of [³²P]orthophosphate and [¹⁴C]serine into lipids of bone and bone cell cultures

1. 1. Calvaria of new-born rats or bone cell cultures were incubated with buffer containing [³²P]orthophosphate or [¹⁴C]serine to study lipid synthesis in mineralizing tissues. 2. 2. [³²P]Orthophosphate was readily incorporated into phospholipids by calvaria and bone cell cultures. As with [¹⁴C]glucose or [¹⁴C]glycerol (ref. 1), lecithin was more heavily labeled than the other phospholipids. The labeling of sphingomyelin and phosphatidyl serine could not be demonstrated from radioactive phosphate. ATP decreased the incorporation of this isotope into lipids. 3. 3. [¹⁴C]Serine gave rise to a variety of radioactive lipids. The synthesis of phosphatidyl serine was enhanced by the addition of both CTP and ATP whereas the labeling of sphingomyelin and phosphatidyl ethanolamine was little affected by these two co-factors.