Developmental Changes in the Distribution of Rat Liver Ribosomes in Response to Dietary Manipulations

Ribosomal profiles were prepared from liver postmitochondrial supernatant preparations of 2- to 21-day-old and 60-day-old rats. Rats fed or starved for 3 or 15 to 16 hours were compared. Relative ribosomal distribution, calculated from planimetric analysis of the hepatic ribosomal profiles, was found to be approximately constant at all ages when fed animals were compared. In contrast, starvation for 15 hours resulted in profound changes in ribosomal distribution, i.e., a relative accumulation of oligosomes as compared with polysomes. This change in ribosomal distribution was most extensive in animals younger than 2 weeks of age, 60-day-old rats showing no effect. Refeeding of 6-day-old starved rats with diets containing 10% protein resulted in a prompt decrease in the planimetric yield of monsomes and disomes. Similarly, dietary protein was shown to be required to prevent accumulation of these two species. It is suggested that it is the response of the ribosomal cycle to starvation that changes with age rather than the maximum capacity for protein synthesis.