[Criteria for indirect evaluation of protein status of organisms]

The value of the determination of blood protein and amino acids is discussed. The results suggest that the serum albumin concentration is perhaps not very sensitive index of the protein value. But the level of plasma amino acids may yield valuable information of the protein state. However, there is no evidence that the use of the plasma amino-acid level as an indicator of the protein value is exclusively profitable. Determination of the urea level in the blood under standardized experimental conditions may be a good indirect estimation of the adequate protein ratio in an individual. Various enzyme activities seem to be no conclusive indices of the state of protein nutrition. A simple determination of the urinary nitrogen might perhaps be a satisfactory method for evaluating the protein quality for an individual. The determination of urinary urea closes not seem to be a more valuable indicator than the protein state. It has been shown that the diameter of the myofibrils depends on the adequate protein ratio in the feed. The weights of several muscles and different organs are also in agreement with the supply of protein. Furthermore, the author discusses the correlation of the nitrogen concentration in a single leg of the rat to that in the total body as a possible indirect method for determining the protein value.