The metabolism of free fatty acids and chylomicron triglyceride fatty acids by isolated rat liver cells

Abstract

1. 1. A study of the uptake and metabolism of chylomicron triglyceride fatty acids and free fatty acids has been carried out in a preparation of morphologically intact isolated liver cells from fasted rats. Cells incubated with chylomicrons in the presence of serum did not take up significant amounts of [ 14C]triglyceride fatty acids and oxidized less than 1% to 14CO 2 and [ 14C]Ketone bodies. When cells were incubated in the absence of serum, the recovery of 14C in the liver lipids was increased 90-fold but oxidation to 14CO 2 and [ 14C]ketone bodies was not significantly increased. These results indicate that the presence of serum in the incubation prevents adherence of chylomicrons to cell surfaces. 2. 2. Significant oxidation of [ 14C]triglyceride fatty acids to 14CO 2 and [ 14C]ketone bodies was observed only when lipoprotein lipase was added to the incubation. When 13 units of lipoprotein lipase were added to the incubation, the recoveries of [ 14C]triglyceride fatty acids in oxidation products were similar to recoveries from [ 14C]free fatty acids. 3. 3. These experiments strengthen the hypothesis that triglycerides are not taken up or metabolized by liver parenchymal cells in amounts that are physiologically significant. Triglycerides are probably metabolized by hydrolysis by lipoprotein lipase in peripheral capillary beds. The reaction products, glycerol and free fatty acids, may then recirculate to the liver in which form they readily cross the liver cell membrane.