Studies on the metabolism of arylacetic acids. 7. The influence of varying dose size upon the conjugation pattern of 2-naphthylacetic acid in the guinea pig, mouse and hamster.

1. The influence of dose size upon the metabolic conjugation of 2-naphthylacetic acid with various amino acids and glucuronic acid has been studied in the guinea pig, mouse and hamster. 2. Guinea pigs conjugated 2-naphthylacetic acid with glycine and glucuronic acid. 3. Mice conjugated 2-naphthylacetic acid with glycine, taurine and glucuronic acid. Taurine conjugation had the highest capacity, and both this and the glycine mechanism were saturated at doses above 100 mg/kg. 4. Hamsters utilized glutamine, glycine, taurine and glucuronic acid for the conjugation of 2-naphthylacetic acid. No conjugation pathway was saturated by doses up to 200 mg/kg. 5. The thus-far unique ability of 2-naphthylacetic acid to evoke multiple amino acid conjugations, using the taurine and glutamine mechanisms hitherto unknown in these species, appears to be due to its affinity for previously unrecognized enzyme systems, rather than to saturation of 'normal' pathways revealing novel routes at high doses.