[Assimilation of certain amino acids administered to animals of different ages]

Changes in the content of some amino acids (tryptophane, lysine, histidine and arginine) in blood plasma were studied in young and old rabbits administered lysine, arginine and urea into the stomach. A decrease in utilization rate of the test amino acids in old animals, their interdependence and the effect of urea administration on the lysine level in blood serum at a relatively stable content of tryptophane and histidine were established. A conclusion is drawn about the necessity of taking into consideration the age features of lysine and arginine assimilation in determining their consumption rates in nutrition and in the use as food additives and medicinal preparations.