Endogenous Formation of Hippuric Acid.

Abstract

Humans and rats receiving a purified laboratory diet excrete hippuric acid in the amount of 1 to 3 mg/kg body weight/day. This amount of hippuric acid appears to be formed endogenously and its excretion in the rat is not affected by fasting, the inclusion of sulfasuxidine in the diet, or the administration of phenylalanine. Only 0.05% of the radioactivity of 3-C14-L-phenylalanlne injected into a rat was excreted in the form of hippuric acid in 24 hours. Further experiments suggested that the endogenous hippuric acid could not be derived from phenylalanine in any direct manner.