| Abstract: | The importance of ethanolamine and sphingosine as precursors of phosphoethanolamine was investigated by incubating them with 3H]glycerol and isolated rat hepatocytes. Sphingosine (0.1--0.5 mM) stimulated the synthesis of phosphatidylethanolamine from 3H]glycerol, but the stimulation by ethanolamine was more pronounced. Furthermore, more phosphoethanolamine accumulated in the heptatocytes after incubation with ethanolamine than after incubation with sphingosine. It is concluded that ethanolamine is the most important phosphoethanolamine precursor in rat liver. Higher concentrations of sphingosine caused accumulation of 3H]phosphatidate and inhibition of total glycerolipid synthesis in isolated hepatocytes, when incubated in the presence of 3H]glycerol. These effects were very similar to those of fenfluramine and norfenfluramine described previously. Simpler cationic amphiphilic amines, like oleoylamine and octadecyltrimethylammonium bromide, also caused these effects. Variation of alkyl chain length and amphiphile charge showed that both a positive charge and a certain alkyl chain length were necessary for interference with phosphatidate metabolism. A much wider range of compounds inhibited total glycerolipid synthesis from 3H]glycerol. |
