Influence of the Dietary Protein Deficiency on the Activities of Ribosomes and Polysome Patterns in Muscle and Liver of Rats

A group of rats weighing about 120 g were killed at the beginning of the experiment and after 10 days on the 20% casein diet (C-0 and C-10 groups), and another group of rats were killed after 1, 2 and 10 days on the protein-free diet (PF-1, PF-2 and PF-10 groups). From muscle and the liver of each group ribosomes were prepared, and the protein synthesis activity and the polysome patterns were investigated. The activity of polysome fractionated into each size was also measured.

Muscle ribosome activity in PF-1, PF-2 and PF-10 groups decreased to about 60%, 40% and 40% of that in C groups, respectively, and this decrease was due to a fall in activity of polysome itself rather than disaggregation of polysome. Liver ribosome activity in PF-1, PF-2 and PF-10 groups were reduced to about 95%, 90% and 65% of that in C groups, respectively. These alterations in PF-1 and PF-2 groups seemed to be in part related to changes in polysome pattern, whereas ribosome activity in PF-10 group was reduced without changes in polysome pattern.