Kinetics of phosphatidylethanolamine biosynthesis from (I,I-3H2)sphingosine in rat liver

Oligodendroglial glycerophospholipid synthesis: incorporation of radioactive precursors into ethanolamine glycerophospholipids by calf oligodendroglia prepared by a Percoll procedure and maintained in suspension culture

Oligodendroglia prepared from minced calf cerebral white matter by trypsinization at pH 7.4, screening, and isosmotic Percoll (polyvinylpyrolidone-coated silica gel) density gradient centrifugation survived in culture on polylysine-coated glass, extending processes and maintaining phenotypic characteristics of oligodendroglia. In the present study, ethanolamine glycerophospholipid (EGP) metabolism of the freshly isolated cells was examined during short-term suspension culture by dual label time course and substrate concentration dependence experiments with [2-3H]glycerol and either [1,2-14C]ethanolamine or L-[U-14C]serine. Rates of incorporation of 3H from the glycerol and of 14C from the ethanolamine into EGP were constant for 14 h. In medium containing 3 mM-[1,2-14C]ethanolamine and 4.8 mM-[2-3H]glycerol, rates of incorporation of 14C and 3H into diacyl glycerophosphoethanolamine (diacyl GPE) were similar. Under the same conditions, 3H specific activities of alkylacyl GPE and alkenylacyl GPE were much lower than 14C specific activities, likely as a result of the loss of tritium during synthesis of these forms of EGP via dihydroxyacetone phosphate. L-[U-14C]serine was incorporated into serine glycerophospholipid (SGP) by base exchange rather than de novo synthesis. 14C from L-[U-14C]serine also appeared in EGP after an initial lag period of several hours. Methylation of oligodendroglial EGP to choline glycerophospholipid (CGP) was not detected.