Studies on Phospholipid Metabolism in Choline Deficient Fatty Liver By AKIRA YAMAMOTO, MOTOYA SANO*

Rats were fed a choline deficient diet and the incorporation of 32PO4, l4CH3-methionine and "CHj-choline into phospholipids was measured. Synthesis of cephalins and the conversion of phosphatidyl-ethanolamine into lecithin through methylation were both decreased in the initial stage. The synthesis of cephalins as well as the synthesis of lecithin through " indirect pathway " were recovered to the control level in the second stage of the fatty liver. Finally, the synthesis of cephalins was again decreased. Administration of methionine resulted in the recovery of the synthesis of cephalins to the control level at 4 and 20 days of feeding, when the synthesis was decreased origi-nally without methionine administration. Methionine is not so effective in releasing fat from the liver as choline is. " Direct pathway " for the synthesis of lecithin seems to be closely connected to the fat releasing mechanism in the liver. Several different pathways have been •proved for the biosynthesis of lecithin in rat liver (/—3). More knowledge is needed to understand the functional relationship be-tween these pathways. Previous work in this laboratory has shown that the difference in fatty acid composition of lecithin is greatly involved in this problem (4). In the present work, changes of phos-pholipid metabolism in rat liver studied in relation to the time period of feeding a choline deficient diet. Observation was also made on the effect of methionine administra-tion in three different stages of the fatty liver. The mechanism of disturbances of phospholipid metabolism in choline deficient fatty liver will be discussed in this paper, in connection with the shift of balance between alternate pathways of synthesis of lecithin and disturbances in protein metabolism