Impaired labelling of liver phosphatidylethanolamine from ethanolamine-14C in choline deficiency

Abstract

Ethanolamine-14C was injected intraportally to eight rats after 3 days of choline-deficient (c.d.) feeding and to eight choline-supplemented (c.s.) rats. The rats were killed in groups of two after 4, 8, 18, and 32 min. Much less 14C was incorporated into phosphatidylethanolamine and phosphatidylcholine in the c.d. livers, while the level of the former phospholipid was increased and the latter was decreased in these livers.The liver water-soluble constituents were separated by anion and cation exchange chromatography and the following components were analyzed : choline, ethanolamine, glycerophosphocholine, glycerophosphoethanolamine, choline phosphate, ethanolamine phosphate, and CDP-ethanolamine. In c.d. liver the levels of ethanolamine and its derivatives were increased while choline and choline phosphate were reduced. There was a lower incorporation of ethanolamine-14C into CDP-ethanolamine in the deficient livers whereas the specific radioactivities of ethanolamine and ethanolamine phosphate were increased. These findings are interpreted as indicating the existence of a block at the CTP : ethanolamine phosphate transferase step of phosphatidylethanolamine synthesis in c.d. liver.