Microbial amino acid metabolites and bladder cancer: no evidence of promoting activity in man.

1. Indole, p-cresol and phenol are microbial amino acid metabolites which show co-carcinogenic or promoting activity in animal studies. Their involvement in the development of human bladder cancer has been determined by measuring the urinary excretion of indican (indoxyl sulphate) and conjugated phenols. 2. Thirty-two patients (22 males, 10 females) with histologically confirmed carcinoma of the urinary bladder and a similar number of age and sex matched controls took part in the study. The excretion of indican, p-cresol and phenol showed wide interindividual variability, but did not differ significantly between the two groups. 3. The findings indicate that these endogenous metabolites do not contribute significantly to the development of human bladder cancer.