Experimental protein-energy deficiency in rats. Ratio of serine+glycine to threonine as an index of deficiency

Abstract

1. Rats were given a low-protein (10 g/kg) diet for 16 weeks and the changes occurring in their serum amino acids were studied; during this time a full picture of protein-energy malnutrition was manifested. Groups of rats were killed at intervals of 4 weeks.2. Food intake decreased gradually from the 4th to the 8th week, then increased slightly from the 9th to the 11th week, and then decreased again.3. The body-weight of the rats fell progressively from the 1st week on the low-protein diet, remained stationary from the 10th to the 13th week, and then decreased again during the last 4 weeks.4. The ratio of non-essential to essential amino acid was not correlated with the severity of protein deficiency.5. The ratios between some individual amino acids were compared with these ratios in control rats during the 4-week periods of protein deficiency. The ratio of serine+glycine to threonine was always significantly higher in the protein-deficient than in the control rats.