Effect of Thiouracil on Free Amino Acids in the Blood Plasma of Chicks

LEVELS of free amino acids as determined in the blood plasma of chicks can be quite variable even though the chicks are fed similar diets and are of the same breed, sex and age (Shao and Hill, 1967; Hill and Olsen, 1963). An unusually high level of lysine and threonine observed in an experiment in which blood was sampled under conditions of extremely high summer temperature (Hill and Olsen, 1965), prompted us to consider the possibility that the metabolic rate of the bird at the time of sampling might influence plasma amino acid levels. As a test of this hypothesis we measured the plasma amino acids following administration of thiouracil at a level which might be presumed to lower metabolic rate (Singh and Shaffner, 1950; McCartney and Shaffner, 1950, 1949; Shaffner and Andrews, 1948). Although the observations in the present paper did not support the above hypothesis they are believed . . .