Change in the level of endogenous sphingosine in cell nuclei from regenerating rat liver

: High-performance liquid chromatography was used to study the changes in the sphingosine content in regenerating rat liver cell nuclei during RNA and DNA synthesis. It was found that activation of nucleic acid synthesis was accompanied by sphingosine accumulation in cell nuclei in parallel with the induction of the sphingomyelin cycle consisting in the increasing activity of sphingomyelinase and alteration of the sphingomyelin and ceramide content. To clarify the mechanism of sphingosine involvement in replication and transcription, the ability of this product to interact with DNA and modify the activity of RNA-polymerase in vitro was studied. At 10(-4) M sphingosine prevented the interaction of acridine orange with DNA and activated the transcription enzymes. Several alternative mechanisms of sphingosine involvement in the control of nucleic acid synthesis are discussed.