The influence of dietary choline intake upon liver ethanolamine metabolism

The effect of dietary choline upon liver ethanolamine metabolism was investigated by measurement of the changes in the liver levels of phospholipids and their precursors and in the metabolism of intraportally administered [14C]ethanolamine which occur when choline feeding is restored to 3-day choline deficient rats. The earliest detectable actions of choline were restoration of the decreased liver phosphatidyl choline level and beginning decreases in the elevated levels of liver ethanolamine, ethanolamine phosphate, CDP-ethanolamine, and phosphatidyl ethanolamine. The impairment at the CTP:ethanolaminephosphate cytidylyltransferase (EC 2.7.7.14) reaction induced by choline deficiency was reversed more slowly than were the increased levels of the ethanolamine-containing intermediates.In a further experiment it was observed that the liver levels of all of the ethanolamine-containing compounds were progressively diminished when the content of dietary choline was increased up to 1.2%. These findings indicate that exogenous choline exerts an effect upon liver metabolism which causes decreases in the liver levels of ethanolamine and its derivatives, including phosphatidyl ethanolamine. The nature of this action of choline is not known. In an experiment where rats were fed a diet containing 1% ethanolamine, the pattern of increase in the levels of the liver ethanolamine-containing substances did not mirror the pattern found in choline deficiency. This suggests that the increases in liver ethanolamine compounds caused by dietary choline deficiency are not due primarily to an excessive accumulation of free ethanolamine.