Distribution of newly formed fatty acids among glycerolipids of isolated perfused rat liver.
Livers of chow fed rats were perfused 1-3 h with buffer, glucose, albumin, and red blood cells, made up in 100 percent D(2)O. Glycerolipids were isolated and the deuterated fatty acids determined by gas chromatography with mass spectrometry on Silar 5 CP. Percentage of replacement by deuterated acids ranged from 1 to 14, of which palmitate was 87 percent. Differences were found in total lipid class and in subcellular distribution of the newly synthesized acids. Microsomes had 37 percent more deuterated acids than the total or floating fat. At 3 h the highest replacement was found in diacylglycerols (17 percent) and free fatty acids (11 percent). Of the palmitate in hepatic choline and ethanolamine phosphatides, 6.9 percent and 4.7 percent, respectively, contained dueterium. The serine and inositol phosphatides had a higher proportion of deuterated palmitate (7.7 percent) than other phosphatides. The data support the hypothesis that palmitate is incorporated into glycerolipids largely via de novo synthesis while stearate enters them by deacylation-acyl transfer replacement.