Synthesis of Phosphatidyl‐dCMP in Human Lymphocytes and Its Enhancement by Chlorpromazine

When phytohemagglutinin‐stimulated lymphocytes are labelled with [ 3 H]deoxycytidine (dCyd), a compound soluble in organic solvents is formed. Several analytical procedures such as thin‐layer chromatography and alkaline hydrolysis of the product obtained after labelling of stimulated lymphocytes with [ 14 C]glycerol and [ 3 H]dCyd, suggest that the product synthesized is phosphatidyl‐dCMP. This compound is synthesized in much smaller amounts than when permeabilized lymphocytes and [ 3 H]dCTP as a precursor are used. The synthesis of phosphatidyl‐dCMP is highly enhanced by chlorpromazine, phosphatidic acid and arachidonic acid, whereas addition of inositol diminishes the amount of detected phosphatidyl‐dCMP. It is suggested that this compound would be a precursor of phosphatidylinositol.