Metabolism of fucoglycoproteins in the developing rat brain

Abstract

The amount of fucose bound to macromolecules in the particulate fraction of rat brain increased only slightly (from 7.7 to 9.9 μmoles/g protein) between the ages of 5 and 26 days. However, the incorporation of intraperitoneally injected [ 3H]fucose into the particulate fraction of brain decreased rapidly with age from the first to the twenty-sixth day after birth. A similar decrease in incorporation with age was also observed after intracerebral injection of the [ 3H]fucose and in vitro with slices of brain cortex. Turnover studies demonstrated that there was no loss of [ 3H]fucose from the brain glycoproteins of 5-day-old rats for 3 weeks following injection, and there was only a slow loss of protein-bound [ 3H]fucose in 26-day-old rats during the same period. However, by injecting non-radioactive fucose to compete with reutilization of [ 3H]fucose which had been released from glycoproteins, it was possible to demonstrate a more rapid turnover of [ 3H]fucose in 5-day-old rats than in 26-day-old rats. These results suggest that part of the greater incorporation of radioactive fucose in the younger animals is due to a greater rate of turnover of the fucose moieties of brain glycoproteins.