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

Abstract

SummaryThe 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 . Th e incorporation by the liver slice of [1-14C] glycerol into PC3 in mito chondria 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 phos phatidylcholine were observed in the intact liver as well as its subcellular fractions. The possible relationship of these changes after fasting to th e similarity in the incorporation pattern of [l-14C] glycerol into the molecula r species of these glycerolipids was demonstrated .Considerable but equivocal information is available concerning the effect of fasting on the concentration of hepatic lipids in rats (1-6) . In the previous ex periments in which the effect of fasting was examined systematically , we have shown that overnight fasting produces a significant increase in hepatic PC and PE but not TG In the liver of male rats (7) . An attempt to determine the fatty acid composition of hepatic subcellular fractions in fasted rats was done by ALLMA N et al. (3) and ROGERS (6). These investigators were , however, concerned only with total lipids or total phospholipids , and not with each class of glycerolipids in