THE QUANTITY OF DIETARY-PROTEIN AFFECTS BRAIN PROTEIN-SYNTHESIS RATE IN AGED RATS

The purpose of this study was to determine whether the quantity of die tary protein affects the rate of brain protein synthesis in aged rats. Experiments were conducted on three groups of 30-wk-old rats fed diet s containing 0, 5 or 20 g casein/100 g for 10 d. The fractional rates of protein synthesis in brain, liver and kidney declined with a decrea se in quantity of dietary protein. In brain, liver and kidney, RNA act ivity [g protein synthesized/(g RNA.d)] was significantly correlated w ith the fractional rate of protein synthesis. The RNA concentration (m g RNA/g protein) was not related to the fractional rate of protein syn thesis in any organ. The results suggest that the rate of protein synt hesis in the brain declines with a decrease in quantity of dietary pro tein in aged rats, and that RNA activity is at least partly related to the fractional rate of brain protein synthesis.