Turnover In Vivo of Lactosyl‐ceramide and Other Glycosphingolipids in the Adult Rat Brain

Abstract

The quantitative contribution of glucose to the biosynthesis of lactosyl-ceramide and other glycosphingolipids was studied in the adult rat brain in vivo using a semicompartmental model. Half-lives of glucose carbon in the total C pool and the carbohydrate residue of the lipid were calculated. In all glycolipids the half-life of carbohydrate units was 6-8 .times. shorter than the half-life of C in the total C pool of the same lipid. This carbohydrate half-life appeared closely related to the turnover rate of the glycolipid. The shortest carbohydrate half-life (2.2 days) was obtained for lactosyl-ceramide followed by gangliosides, galactosyl-ceramides, and sulfatides. Lactosyl-ceramide may serve as a branch point for the biosynthesis of cerebral gangliosides in vivo, not as a breakdown product of more complex molecules.