1975 Volume 49 Issue 4 Pages 197-203
Male rats weighing about 120g were killed after 1, 2, 4 and 10 days on a protein-free diet, and in vitro synthesis of protein was measured by the incorporation of 14C-glycine into protein of isolated soleus muscle and liver slices.
The rate of muscle protein synthesis fell rapidly to about 40% of the initial control value until the 2 nd day, and then was reduced less rapidly to about 25% of the control value on the 10 th day. Muscle protein synthesis rate per unit of RNA dropped suddenly to about 60% of the control value on the 1 st day and then was reduced gradually to about 50% and 40% of the control value on the 4 th and 10 th day respectively.
In the liver, the rate of protein synthesis increased to the 2_??_3 times of the initial control value on the 1 st and 2 nd day, and thereafter began to decline, but was still higher on the 10 th day than the control value. These alterations in the liver were caused mainly by the changes in the incorporation activity per unit of RNA.
By comparing these present results on 120g rats with our previous results on 200g and 400g rats, it was suggested that muscle protein synthesis decreased more quickly and more greatly in the protein deficiency as rats were younger.