Metabolism of phosphatidyl-dCMP in sarcoma 180 cells. Effect of chlorpromazine, phosphatidic acid and inositol.

The synthesis and degradation of phosphatidyl-dCMP was studied in intact and permeabilized Sarcoma 180 cells as well as in isolated nuclei. It was verified that chlorpromazine greatly enhanced phosphatidyl-dCMP synthesis and completely abolished its hydrolysis in intact cells. The former effect was reversible and was partially lost upon permeabilization or isolation of nuclei. Phosphatidic acid also increased liponucleotide synthesis and the combination of phosphatidic acid with chlorpromazine was not additive. When inositol was added to cells which had accumulated phosphatidyl-[3H]dCMP, the recovery of radioactivity in the organic phase decreased; this effect was dose-dependent and specific for inositol, and was accompanied by an increased release of [3H]dCMP to the cell medium. In isolated microsomes, addition of Ptd-dCMP determined incorporation of [3H]inositol into phosphatidyl-inositol. These results strongly suggest that phosphatidyl-dCMP is utilized for the synthesis of phosphatidyl-inositol.