THE DETERMINATION OF ARGININE IN DOG BLOOD

Arginine is the only known amino acid which possesses a guanidine group.It is the only guanidine derivative which is present in significant amounts in our diet, occurring in all proteins whose composition has been determined.For this reason, it has been considered as a possible precursor of creatine and the purines.One phase of the metabolism of arginine is its hydrolytic decomposition by the enzyme arginase, present in the liver, into urea and the diamino acid, ornithine.The work of Thompson (1905) who studied the rate of urea excretion in dogs following the administration of arginine, and of Felix and Tomita (1923) on the rate of destruction of arginine perfused through the surviving liver of cats, indicates that the guanidine group of the greater part, at least, of ingested arginine is quickly split off.Whether a small portion of ingested arginine is metabolized in another manner, is not known.The specific character of the activity of arginase is illustrated by the paper of Felix, Muller, and Dirr (1928).Derivatives of arginine in which the carboxyl group is involved or in which the amino group is removed, no longer react with arginase.Therefore, if deaminization took place prior to the action of arginase on a portion of ingested arginine, the guanidine group would be protected against the action of arginase.In this connection may be mentioned the work of Bunney and Rose (1928), which indicates the ability of the animal organism to synthesize arginine as measured by the rate of growth in rats fed on diets from which arginine had been removed as completely as possible.Abderhalden (1913) isolated arginine from blood.However, no methods have been available for studying the arginine content