Choline regulates phosphatidylethanolamine biosynthesis in isolated hamster heart

The effect of choline on phosphatidylethanolamine biosynthesis in the isolated hamster heart was investigated. Hamster hearts were perfused with [2-14C]ethanolamine in the presence of 0-0.5 mM choline. Incorporation of label into phosphatidylethanolamine was decreased 28% at 0.2-0.5 mM choline. Analysis of the ethanolamine-containing metabolites of the CDP-ethanolamine pathway revealed that choline (0.2-0.5 mM) in the perfusate had no effect on the labeling of ethanolamine. However, a 28-30% reduction in the labeling of phosphoethanolamine and CDP-ethanolamine was observed. Concurrently, there was a 2-fold increase in the intracellular choline level. Although the formation of CDP-ethanolamine is regarded as the rate-limiting step for phosphatidylethanolamine biosynthesis, choline was found to inhibit ethanolamine kinase, but did not have any effect on phosphoethanolamine cytidylyltransferase. Hence, choline may provide an additional mechanism for the regulation of phosphatidylethanolamine biosynthesis.