Turnover of phosphocholine and phosphoethanolamine in ether-phospholipids of Krebs II ascite cells.

Krebs II ascite cells suspended in Eagle medium were incubated at 37 C for up to 6 hr in the presence of [3H] glycerol or [32P] orthophosphate. After extraction, their lipids were treated with guinea pig phospholipase A1 under conditions where all diacyl-phospholipids (diacyl-PL) became hydrolyzed with 55% recovery of lyso-PL. Using a bidimensional thin layer chromatography (TLC) involving exposure to HCl fumes between the two runs, it then became possible to determine at once the specific radioactivity of the three subclasses (diacyl-, alkylacyl- and alkenylacyl-) present in choline glycerophospholipids (CGP) and ethanolamineglycerophospholipids (EGP). Compared to diacyl-PL, a lower de novo synthesis of ether subclasses was evidenced in both CGP and EGP by [3H] glycerol incorporation. Although the same profile was obtained for CGP with [32P] orthophosphate, the three EGP subclasses displayed in this case the same specific radioactivity. These data indicate a higher turnover rate of the polar head group of ether-EGP compared to either-CGP. The simple methodology used in the present study might thus prove helpful in developing enzymatic studies dealing with the mechanism of this accelerated renewal.