EFFECTS OF PROTEIN DEFICIENCY ON THE RATE OF RADIOACTIVITY LOSS FROM BODY CONSTITUENTS IN ADULT RATS GIVEN ¹⁴C-AMINO ACIDS

Abstract

The effect of protein deficiency on the rate of loss of radioactivity from body constituents was studied in adult rats administered ¹⁴C-Chlorella protein hydrolysate or ¹⁴C-lysine. Rats were kept on a protein-free diet for 3 weeks and then injected with labelled amino acids and fed on a protein-free diet for 3 more days to allow ¹⁴C deposition in tissues. Then they were given experimental diets (protein-free diet, 1% and 10% wheat gluten diets pair-fed with the protein-free diet, and 10% wheat gluten diet ad libitum) for 7 days and sacrificed.
The rates of loss of radioactivity from tissue proteins became low in general with the extent of protein deficiency. This increased capacity of tissues to retain ¹⁴C-amino acids may result from higher efficiency of protein utilization in protein deficiency. The reutilization of free amino acids and the rate of catabolism of tissue proteins are discussed on the basis of the results. The half-life of muscle protein was too long to observe the effects of experimental diets given for 7 days on the rate of loss of radioactivity.