Glycerolipid metabolism in cellular and subcellular fractions of fasted rat liver.

The effect of overnight fasting on glycerolipids of the rat liver organelles was studied. The concentration of microsomal phospholipids was markedly decreased by fasting, whereas that of mitochondria and whole liver increased significantly. The significant increase due to fasting in the activity of microsomal phosphorylcholine-glyceride transferase appeared to be responsible for the increased concentration of hepatic phospholipid. The incorporation by the liver slice of [1(-14)C] glycerol into PC3 in mitochondria was increased by fasting, while there was no difference in the microsomal fraction containing supernatant. The significant decrease in the relative proportions of oleic and linoleic acids and a significant increase in stearic and arachidonic acids in phosphatidylcholine were observed in the intact liver as well as its subcellular fractions. The possible relationship of these changes after fasting to the similarity in the incorporation pattern of [1(-14)C] glycerol into the molecular species of these glycerolipids was demonstrated.