Protein synthesis, net deposition and breakdown was studied in the gastrocnemius muscles of growing rats between weaning and 90 days of age. 2. Fractional protein synthetic rates declined from 30.02% at 25 days to 7.41% at 90 days. 3. The rate of protein degradation follows a similar pattern to that of protein synthesis. A linear relationship was found. 4. The break in the growth curve between 30 and 31 days was also observed in protein metabolism.
