Phospholipid Metabolism in Ehrlich Ascites Tumor Cells. II. Turnover Rate of Ether Phospholipids

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Abstract
1. Radioactive precursors of phospholipids, i.e., 82P1, [1–14C]glycerol, [2–3H]glycerol, and [1–14C]acetate, were individually injected into the peritoneal cavity of mice bearing Ehrlich ascites tumor cells and the rates of incorporation were estimated. 2. Although [2–3H]glycerol was not practically incorporated into ether phospholipids, the other three radioactive precursors were incorporated into diacyl, 1–O-alkenyl-2-acy1-, and 1-O-alkyl-2-acyl-GPE (GPC). 3. In the experiments on 32P1 or [1–14C]acetate incorporation, 1-O-alkyl compounds in the ethanolamine phosphoglyceride fraction showed high specific activities in comparison with 1-acyl compounds. In the case of [1–14C]glycerol incorporation, a high rate of incorporation into 1-O-alkyl compounds was not found. In the choline phosphoglyceride fraction, a high rate of incorporation of the above precursors into 1-O-alkyl compounds was not observed. 4. The specific activities of 1-O-alkenyl compounds were fairly low compared with those of 1-acyl- and 1-O-alkyl compounds throughout the incorporation experiments with [1–14C]glycerol and [l-14C]acetate, but in 32P1 incorporation, 1-O-alkenyl compounds showed higher specific activities than 1-acyl compounds in ethanolamine phosphoglyceride, suggesting an exchange reaction of the phosphorylethanolamine moiety. 5. From the above findings, it appears that alkyl ether phospholipids of ethanolamine form may have a significant role in ascites tumor cells, based on their rapid turnover.