Change of choline metabolism in rat liver on chronic ethionine-feeding.

On chronic ethionine-feeding (0.1% DL-ethionine in 0.5% sucrose solution) for 2, 4 or 6 months, choline metabolism in rat hepatic cells was altered considerably, although RNA contents were virtually unchanged. Choline dehydrogenase activity in the hepatic mitochondrial fraction was suppressed by about 1/2 or 1/3, compared to its normal level, whereas choline kinase activity, which existed in the cytoplasmic fraction, was elevated more than 1.5-fold. The normal value for choline-metabolizing enzymes in terms of the choline dehydrogenase/choline kinase activity ratio was estimated to be about 70 under the defined conditions, while the average value of the activity ratio drastically changed to about 10-20 on chronic ethionine-feeding. The present results suggest that an alteration of hepatic choline-flux occurred, due both to an increase in choline kinase activity and to a counteractive decrease in choline dehydrogenase activity.