Lecithin depletion in hepatic microsomal membranes of rats fed on a choline-deficient diet.

Abstract

Abstract Total, rough and smooth microsomes were isolated from the liver of rats fed on a choline-supplemented or a choline-deficient diet for 24 hr. Some of the preparations were subjected to washing procedures in order to eliminate the luminal contents of, and materials absorbed to, the microsomal vesicles. The neutral lipid and phospholipid composition of the various preparations was determined. A marked depletion of lecithins was found to occur in liver microsomes of rats fed on the choline-deficient diet. In the same animals, the content of cholesterol and of triglycerides was decreased in rough microsomes but increased in smooth microsomes. There was also a shift toward more unsaturated lecithins in total microsomes. These findings indicate that feeding a choline-deficient diet to rats can result in alterations of structural lipoproteins, such as those of the microsomal membranes of hepatocytes, as well as of soluble lipoproteins, such as the VLDL of plasma. As a consequence of the latter, a fatty liver develops. The alterations of the microsomal membranes appear instead to be responsible for other functional derangements, such as the delay in the intracellular transport of albumin, observed in the liver of rats fed a choline-deficient diet. Metabolic reactions catalyzed by enzymes having a functional requirement for phospholipids may be also influenced by the changed lipid composition of the microsomal membranes.