Studies on Phospholipid Metabolism in Bile Duct-Ligated Rat Liver

In the past several years, it has been reported that bile acids accelerate the biosynthesis of biliary phosphatidylcholine. The present study was undertaken to clarify the effects of bile on phospholipid metabolism in the liver. Using 32P-inorganic phosphate, the following facts were confirmed in the liver of bile duct-ligated rats. (1) A significant biosynthesis of phospholipids was observed in the liver of rats on the 2nd day after ligation. This period was found to correspond to the time when the amount of phosphatidylcholine greatly increased in the plasma. These results indicate that the increased phospholipids in plasma are due to the increased biosynthesis of phospholipids in the liver. (2) The enhanced biosynthesis was shown in every phospholipid. The results from the investigation on molecular species of phosphatidylcholine show that the synthesis of phosphatidylcholine is increased in every type of molecular species which is supplied to the bile, liver cell and plasma lipoproteins. (3) In spite of the increased biosynthesis of phospholipids in the liver, the concentration of phosphatidylcholine was decreased, in contrast to the increase of phosphatidylethanolamine. These phenomena indicated that phosphatidylcholine was rapidly released into the plasma right after the synthesis was accelerated by action of the biles accumulated in the liver. On the other hand, phosphatidylethanolamine was not released into the plasma. This result also supports our previous data that phosphatidylethanolamine did not increase in the plasma of bile duct-ligated rats