STUDIES ON ROLE OF PHOSPHOLIPIDS IN TRIGLYCERIDE CYCLE .1. PHOSPHOLIPID SYNTHESIS IN LIVER AND PLASMA OF ETHIONINE-TREATED RATS

A single administration of dl-ethionine to rats was found to initiate a rapid accumulation of triglyceride in the liver while plasma and liver phospholipid (PL) levels decreased. As measured by the incorporation of intravenous NaH2P32O4 at several time intervals after a single administration of ethionine, the drug decreased the specific activity (SA) of liver and plasma phospholipid phosphorus (PLP). At early time intervals after the injection of ethionine this occurred to a greater extent in the plasma than in the liver. Hence, the relative specific activity (RSA) of plasma to liver PLP was decreased initially by ethionine. As a measure of the exchange of PL between plasma and liver, this change in the RSA indicates decreased mobilization of PL from the liver to the plasma following ethionine inhibition of PL synthesis by the liver. Subsequently, the RSA increased, that is, an increased mobilization of PL occurred under conditions of fasting several hours after ethionine administration. Thus, it appeared that remobilization of liver PL tends to occur following the hepatic triglyceride accumulation brought about by inhibition of PL synthesis in the liver. However, remobilization of liver PL occurred also in male rats given ethionine and in fasted rats which did not show accumulation of hepatic triglyceride. These data suggest that phospholipid turnover and transport play an active role in the triglyceride cycle which is activated by fasting and during the recovery phase following ethionine administration. © 1969 The American Oil Chemists' Society.