METABOLISM OF PHOSPHONIUM CHOLINE BY RAT-2 FIBROBLASTS - EFFECTS OF MITOGENIC STIMULATION STUDIED USING P-31 NMR-SPECTROSCOPY

Phospholipid turnover increases with both mitogenic stimulation and on cogenic transformation (1-9). Recent P-31 nuclear magnetic resonance ( NMR) spectroscopy studies of human tumors, animal tumor models and cel l systems have reported elevated phosphomonesters with growth and onco genic transformation, as well as changes in these levels associated wi th treatment (10). In order to gain insights into the mechanisms under lying these changes, we used a phosphonium analog of choline and P-31 NMR spectroscopy to study choline metabolism in quiescent and mitogeni cally stimulated Rat-2 fibroblasts. Cell growth status of these cells has a significant effect on choline metabolism. While overall uptake o f the analog was similar in both quiescent and growing cells, distribu tion among metabolite pools differed. Quiescent cells accumulate label in the phosphodiester pool, with little or none in the phosphomonoest er pool. On the other hand, mitogenic stimulation resulted in a signif icant fraction of the label in the phosphomonoester pool.