PROTEIN SYNTHESIS IN VITRO IN RAT BRAIN AFTER SHORT-TERM PROTEIN STARVATION AND REFEEDING

Rats were fed a protein-free diet for 4 or 6 days. They were compared with rats kept on the same diet for 3 or 5 days and on adequate protein for one additional day. The incorporation of ¹⁴C-labelled amino acid into protein was studied in systems containing ATP, GTP, phosphoenolpyruvate, pyruvate kinase and if required, a mixture of unlabelled amino acids and either the 6000 g supernatant fraction of a brain homogenate or microsomes and soluble enzymes. The 6000 g supernatant fraction showed variation in amino acid incorporating activity as well as in RNase activity as measured by breakdown of labelled polyuridylic acid. There was no difference in RNase activity in isolated microsomes, but the amino acid incorporating activity was significantly higher in preparations obtained from rats fed one meal of protein after 5 days of protein-starvation.