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.