Distribution of Newly Formed Fatty Acids Among Glycerolipids of Isolated Perfused Rat Liver

Abstract

Livers of chow fed rats were perfused 1–3 h with buffer, glucose, albumin, and red blood cells, made up in 100% D2O. 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%. Differences were found in total lipid class and in subcellular distribution of the newly synthesized acids. Microsomes had 37% more deuterated acids than the total or floating fat. At 3 h the highest replacement was found in diacylglycerols (17%) and free fatty acids (11%). Of the palmitate in hepatic choline and ethanolamine phosphatides, 6.9% and 4.7%, respectively, contained dueterium. The serine and inositol phosphatides had a higher proportion of deuterated palmitate (7.7%) 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.