CHOLINE DERIVED FROM THE PHOSPHATIDYLCHOLINE-SPECIFIC PHOSPHOLIPASE-DIS NOT DIRECTLY AVAILABLE FOR THE CDP CHOLINE PATHWAY IN PHORBOL ESTER-TREATED C3HL0T1 2 CL-8 FIBROBLASTS/

We have shown that 12-O-tetradecanoylphorbol 13-acetate (TPA) increase s protein kinase C (PKC)-mediated choline transport, incorporation of choline into phosphatidylcholine (PtdCho) and PtdCho degradation by ph ospholipase D (PLD) in C3H10T1/2 C1 8 cells. Dual prelabeling experime nt using [H-3]/[C-14]choline indicated that intracellular choline gene rated from the PLD reaction was not directly recycled to PtdCho synthe sis within the cell, and that a large fraction of the choline was tran sported out of the TPA-treated cells. In contrast, medium derived chol ine was preferably channeled to PtdCho synthesis. These results indica te that in TPA-treated cells, the choline derived from the PKC-mediate d increased PLD activity and the choline newly taken up by the cell be have as two distinctly different metabolic pools.