RATES OF LOCAL CEREBRAL PROTEIN-SYNTHESIS IN THE RAT DURING NORMAL POSTNATAL-DEVELOPMENT

The degree of recycling of leucine derived from protein breakdown into the precursor pool for protein synthesis was measured in rat brain at different postnatal ages, and age-specific values were used in the ca lculation of regional (local) rates of cerebral leucine incorporation into protein (lCPS(leu)) in 44 brain regions and the brain as a whole. Early in development, a greater fraction of the precursor leucine poo l is derived from protein breakdown, indicating that protein degradati on is higher in young rats compared with adults. In whole brain and in most regions, values for lCPS(leu) were highest at 10 days and gradua lly decreased with age. By 60 days of age, values in cortex were simil ar to 60% of those at 10 days of age. In the paraventricular and supra optic nuclei of the hypothalamus, however, lCPS(leu) increased during development, reaching peak values in adults. In white matter of the ce rebellum and the cerebrum, peaks of lCPS(leu) were reached at 14 and 2 1 days, respectively, approximately at the times of maximum rates of m yelination.