Effect of calorie restriction and protein deficiency on protein metabolism in rats.

The changes induced by the deficiency of calories or nitrogen on the protein metabolism in rats were investigated. Animals were fed either a restricted normal diet, a protein-deficient diet or control diet ad libitum. Rats receiving protein-free diet failed to grow, while the growth of animals given restricted diet was less than those fed ad libitum. Despite that, the dietary deficiency of either calories or proteins caused the loss of protein and increased the incorporation of 1-C14 glycine into liver proteins. The contents of liver-free amino acids and urea were significantly increased only in the protein-deficient rats.