Biosynthesis of molecular species of hepatic glycerophosphatides during metabolism of [1,1-2H2]ethanol in rats.

Rats were injected with [1,1-2H2]ethanol once every hour for 3-48 h and the fatty acid composition of and deuterium incorporation into different classes of hepatic phosphatidylcholines, phosphatidylethanolamines, phosphatidylserines and phosphatidylinositols were determined. Phosphatidylcholines and phosphatidylethanolamines with an oleoyl or a docosahexaenoyl residue at C-2 increased, while many of the species with a linoleoyl or an arachidonoyl residue at C-2 decreased throughout the experiment. No changes were seen in the phosphatidylinositols. The distribution of deuterium between the different positions of the glycerol moiety of the glycerophosphatides was similar for all species studied. The deuterium excess in molecules synthesized de novo was also similar for all species and remained relatively constant throughout the experiment. The mean excess was 8 atom% at C-1, 36 atom% at C-2 and 22 atom% at C-3 of the glycerol moiety. The apparent half-life times calculated for the glycerol moieties were different for the individual molecular species and varied between 1.1 and 36 h. However, the observed half-life times for the corresponding species of the different glycerophosphatides usually were similar. The deuterium excess in hepatic sn-glycerol 3-phosphate synthesized de novo was 8 atom% at C-1, 28 atom% at C-2 and 13 atom% at C-3. The excess at C-2 and C-3 was lower than that of the glycerol moiety of glycerophosphatides, indicating that a specific pool of sn-glycerol 3-phosphate with a gluconeogenetic origin was used for the biosynthesis of the different glycerophosphatides, and that the formation of this pool was closely coupled to ethanol oxidation. The deuterium excess in sn-glycerol moiety of the phosphatidylcholines indicated that these molecules had long half-life times or that the labelling of their precursor increased throughout the experiment.