Phospholipid Metabolism in Ehrlich Ascites Tumor Cells

I. Turnover Rate of Phosphatidylinositol

Abstract

1. Radioactive precursors, ³²P₁ [1-¹⁴C] glycerol, and [1-¹⁴C] acetate, were individually injected into the peritoneal cavity of mice bearing Ehrlich ascites tumor, and the rates of incorporation into phospholipid fractions of Ehrlich ascites tumor cells were estimated. Although no distinct difference in specific activities was observed between phosphatidylinositol and other phospholipid classes as regards the incorporation of [1-¹⁴C]acetate or [1-¹⁴C]glycerol, a higher rate of incorporation of ³²P₁ into phosphatidyl-inositol was observed. The specific activity of phosphatidylinositol reached more than ten times that of phosphatidylcholine in the first hour.
2. The radioactivities incorporated into the phospholipids of Ehrlich ascites tumor cells and liver were estimated after simultaneous injection of ³²P₁, and [2-3H]inositol. The incorporation of 32P, into phosphatidylinositol of liver was similar in specific activity to those of other phospholipids. The ratio (³H/³²P₁) of phosphatidylinositol decreased only slightly in the ascites tumor cells, while an appreciable decrease of the ratio was observed in the liver during the first 3 hr.
3. These results suggest that phosphatidylinositol synthesis through pathways other than de novo synthesis is rapid in ascites tumor cells.