A comparison of the molecular specificities of whole cell and endonuclear phosphatidylcholine synthesis.

Deuterated choline-d(9) labelling of IMR-32 cells enabled comparison of the molecular specificities of whole cell and endonuclear phosphatidylcholine synthesis after 96 h polyunsaturated fatty acid supplementation. Surprisingly, while cell phosphatidylcholine synthesis and remodelling reflected a pattern of polyunsaturated fatty acid accretion, the saturated endonuclear phosphatidylcholine pool was only transiently labelled with polyunsaturates. Periodic endonuclear accumulations of the lipid second messenger diacylglycerol, mobilised from unsaturated phosphatidylinositol or saturated phosphatidylcholine, accompany cell proliferation. Non-specific incorporation into endonuclear phosphatidylcholine and selective removal or remodelling of unsaturated molecular species may form part of a single 'off switch' recycling all endonuclear diacylglycerol accumulations.