Studies on tryptophan metabolism in Danish bladder cancer patients.

Urinary excretion of metabolites of the kynurenine pathway before and after a loading dose of 2 g L-tryptophan was studied in 31 bladder cancer patients from the Copenhagen area. Only 2 patients (6 per cent) showed abnormal tryptophan metabolism, and both patients excreted increased amounts of only 3-hydroxykynurenine after a loading dose of 2 g L-tryptophan. The percentage of bladder cancer patients with abnormal tryptophan metabolism is compared with the percentage found in other parts of the world. It is suggested that these findings may indicate that tryptophan metabolites do not play a major role in the genesis of bladder cancer among bladder cancer patients from the Copenhagen area. Other etiologic factors should be looked for.