The turnover of myelin in the adult rat

Abstract

The rate of loss of radioactivity of lipids of brain subcellular fractions was followed for 56 days after injection of adult rats with uniformly labeled [ 14C]glucose. Myelin did not reach its maximum specific activity until 5 days after injection, then showed a slow rate of loss of radioactivity. When the turnover of the lipid components of purified myelin was measured, inositol phosphatide and lecithin were found to have a more active metabolism than the other myelin lipids which include serine phosphatide, sphingomyelin, ethanolamine phosphatide, cerebroside, cerebroside sulfate, and cholesterol. These results which agree with our previous findings indicate that the metabolism of myelin on the outer layers is identical to that laid down early in the life of the animal. Proteolipid protein showed a half-life of about 35 days, thus was one of the more active myelin components. The pattern of metabolism, though on a longer time scale in myelin, is similar to that of the most active brain membrane fraction. These results are discussed in relation to the possible structure of myelin membranes.