In vivo studies on glycosphingolipid metabolism in porcine blood
Journal of Biological Chemistry
Porcine plasma and erythrocytes were found to contain the same glycosphingolipids as humans, namely glucosyl ceramide, lactosyl ceramide, galactosylgalactosylglucosyl ceramide, and globoside, and the actual concentrations were very similar. The in viva studies were carried out by using uniformly labeled 1%D-glucose as the isotopic precursor and isolating the glycolipids from 30-ml samples of blood removed at frequent intervals over the 3-month study period. The results suggested that
... ted that erythrocyte lactosyl ceramide, galactosylgalactosylglucosyl ceramide and globoside were synthesized in the bone marrow, did not exchange with their plasma counterparts, and were released into the plasma at the time of general erythrocyte catabolism. Erythrocyte glucosyl ceramide did not appear to be synthesized in the marrow and was in dynamic equilibrium with plasma glucosyl ceramide. The label was rapidly and randomly incorporated into all the plasma glycosphmgolipids but after 9 days no labeling could be detected until the erythrocytes began to be catabolized (50 to 70 days). The relative amounts of label in the glycolipids during the 1st week and the latter period from 40 to 60 days confirmed that the rapid source of plasma glycosphingolipid biosynthesis is a minor pathway and showed that the release or catabolism of erythrocyte glycosphingolipids (especially globoside, the major component) is the major source of all four plasma glycosphingolipids.