Protein degradation rates in regions of the central nervous system in vivo during development.

The rate of protein degradation was estimated in several regions of rat brain at various ages by subtracting the rate of accumulation of protein from the rate of synthesis. The rate of degradation in cerebral hemisphere, which was 1.3%/h at 2 days of age, declined steadily with age, approaching the synthesis rate is about 30 days of age (0.8%/h). Degradation rates in the pons medulla, mid-brain and spinal cord were of a similar order to that in the cerebral hemisphere. The cerebellum had an exceptionally high rate of degradation in young rats, 1.9%/h at 2 days of age, which complemented its high rates of synthesis and accumulation. The degradation rate in the young was 2-2.5 times the rate in older rats and was approx. 65% of the synthesis rate during the more active phase of growth. The rapid accumulation of protein in the nervous system during the first week post partum was accompanied by high rates of breakdown, and was the result of a relatively small difference between that high rate of degradation and an even higher synthesis rate.