Regulation of phospholipid metabolism in differentiating cells from rat brain cerebral hemispheres in culture. I. Uptake and phosphorylation of [U-14C]ethanoloamine and the effect of various inhibitors.

Cultured dissociated cells from rat embryo cerebral hemispheres were incubated with [U-14C]ethanolamine and the resulting cellular labeled products were identified. A highly efficient uptake for ethanolamine with a Km of approximately 8.3 muM was calculated. A rapid labeling of phosphorylethanolamine was observed prior to the appearance of label in lipids. A lag period of 2.5 min for the phosphorylation reaction was observed, followed by an almost linear rate for up to 40 min. After a 1-min incubation, a plateau for free ethanolamine taken up by the cells was established. Respiratory inhibitiors such as cyanide, 2,4-dinitrophenol, and N-ethylmaleimide decreased by the formation of phosphorylethanolamine. However, the amount offree ethanolamine present in the cells increased 1.6-fold after 10 min of incubation with N-ethylmaleimide. 2-Chloroethylamine, a structural analog of ethanolamine, and choline were both competitive inhibitiors with an apparent Ki of 0.1 mM and 0.36 mM, respectively. Incubations of short duration suggest that both compounds affect ethanolamine transport into the cells. Based on these studies it is suggested that ethanolamine transport and the phosphorylation reaction are independent events. Evidence based on studies with hemicholinium-3 and chloroethylamine suggest that ethanolamine uptake may proceed by a pathway independent of either choline or serine uptake.