Abstract
Evidence from clinical and experimental studies suggests that certain urinary tryptophan metabolites may play a role in human bladder carcinogenesis. Five metabolites of this essential amino acid—kynurenic acid, acetyl-L-kynurenine, L-kynurenine, 3-hydroxy-L-kynurenine, and 3-hydroxyanthranilic acid—were reported as occurring in elevated quantities in the urine of some patients with urinary bladder cancer. When the pellet implantation technique was employed, an augmented incidence of bladder carcinomas was observed in mice exposed to 3-hydroxy-L-kynu-renine, 3-hydroxyanthranilic acid, xanthurenic acid, the 8-methyl ether of xanthurenic acid, and 8-hydroxyquinaldic acid. These compounds interact with the bladder, pass across it easily, and seem to require the presence of at least one other factor for the complete expression of bladder carcinogenicity.