Studies on the Regulation of Choline Uptake and Phosphatidylcholine Biosyntbesis

The effects of amino acids,ethanolamine and monomethylethanolamine on choline uptake and phosphatidylcholine biocynthesis in baby hamster kidney(BHK-21) cells were investigated.The uptake of labelled choline was noncompetitively inhibited by amino acids.The conversion of choline to CDP-choline and subsequently phosphatidyloholine was not affectid by the presence of amino acids.The uptake of choline was also competitively inhibited by ethanolamine.Although ethanolamine is a potent inhibitor of choline kinase,the conversion of choline to phosphocholine was not affected.Ethanolamine did not change the pool anes ofphosphoeholine and CDP-choline.As judged by the speeifie radioactivity of CDPcholine and the labelling of phosphatidylclioline,the rates of phosphatidylcholine biosynthesis were not significantly different between the control and the ethanolamine-treated cells.Monomethylethanolamine was more powerful in inhibiting choline uptake than ethanolamine,and also inhibited the activitied of choline kinase and CTP:phosphocholine cytidilyltransferabe.These results suggested that not only choline uptake, but abso the conversion of choline-containing compounds for the biosynthesis of phosphatidylcholine were disturbed by monomethylethanolamine.