The turnover of molecular species of phosphatidylinositol in Ehrlich ascites tumor cells.

It has been shown previously the 32Pi is incorporated into phosphatidylinositol 30 times faster than into the other phospholipids classes in Ehrlich ascites tumor cells, whereas [1-14C] glycerol is incorporated at almost the same rate (Waku, K., Nakazawa, Y. and MOri, W. (1976) J. Biochem. 79, 407-411). It was therefore suggested that there is a recirculating system (phosphatidylinositol leads to diacylglycerol leads to phosphatidic acid leads to CDP diacylglycerol leads to phosphatidylinositol) of phosphatidylinositol in Ehrlich ascites tumor cells. In this work, 32Pi or [1-3H] glycerol was injected into the peritoneal cavity of mice bearing Ehrlich ascites tumor cells from which the lipids were extracted after selected periods. Phosphatidylinositol was prepared and fractionated in the form of dimethylphosphatidic acid into six molecular species by AgNO3-impregnated TLC. The specific radioactivities of the fractionated species were determined. 32Pi was incorporated into diene molecular species and [1-3H] glycerol into monoene species with a higher rate than the other species and both precursors were incorporated into tetraene species rather slowly. 32P/3H values appeared to be at almost the same for each molecular species, although monoene species showed slightly lower values. These results suggest that there could be a recirculating of the phosphorylinositol moiety in each of the molecular species of phosphatidylinositol.