A new aspect of the urinary excretion of tryptophan metabolites in patients with cancer of the bladder

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Abstract
Metabolites of the amino acid tryptophan have been suspected of being involved in the genesis of human urinary bladder cancer. It was suggested that a neoplastic change could result from increased urinary excretion of tryptophan metabolites. From studies in which the excretion of metabolites was assessed after loading the patients with L‐tryptophan it was concluded that abnormalities in tryptophan metabolism are causing the elevation of metabolite excretion. The present study however, which measured basal excretion of metabolites, demonstrates that the presence of tumor in the urinary tract must be considered as causative for elevations of metabolite excretion. An improved method for determining the spontaneous metabolite excretion is described. The metabolites kynurenine, kynurenic acid, 3‐hydroxykynurenine, xanthurenic acid and 3‐hydroxyanthranilic acid were determined in 165 urine samples obtained from bladder cancer patients, renal cancer patients, patients cured of bladder cancer and control subjects. Thirty six percent of the bladder cancer patients and 67% of the renal carcinoma patients excreted abnormally high amounts of at least one of the metabolites. It was observed that in bladder cancer an elevated excretion of metabolites occurred principally in patients with obstruction to the outflow of urine from the kidneys. Ureteral obstruction, probably a direct consequence of the presence of tumor in the urinary tract, causes an alteration in renal function which is reflected in urea and creatinine retention. The high incidence of abnormal excretion of tryptophan metabolites in renal cancer also points to alterations in renal function caused by the presence of tumor.

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