Rates of protein synthesis in brain and other organs.

We previously found a decrease in protein synthesis in brain during development, which was much greater as measured in brain slices than in brain in vivo. In the present work such changes in brain were compared to those in other organs. With measurement of incorporation of flooding doses of [14C]valine into proteins of organs, the highest synthesis rate in the adult animal in vivo was found in liver (2.2%) followed by kidney (1.8%), spleen (1.6%), lung (1.0%), heart (0.7%), brain (0.6%) and muscle (0.5%). In immature animals the synthesis rate was highest in spleen (2.6%) followed by liver (2.4%), kidney (1.7%), lung (1.6%), brain (1.5%), heart (1.1%), and muscle (0.9%). Protein synthesis in slices from each tissue proceeded at lower rates than in vivo, especially in adults. The tissue affected the most by the preparation of the slices was muscle.