Suppression of dibutylnitrosamine-induced bladder carcinomas in hamsters by dietary indole

Effect of dietary indole on the urinary bladder tumorigenesis by chronic dibutylnitrosamine (DBN) treatment was evaluated in hamsters. In the first experiment, in which DBN-water and diet were given ad libitum, dietary indole significantly suppressed bladder tumor incidence. The inhibitory effect was more pronounced in males. In the second experiment, in which consumption of both diet and DBN-water was rigidly controlled by pair-feeding, dietary indole again significantly suppressed bladder tumor incidence; its effect was similar in both males and females. This suppressive effect of indole on bladder tumorigenesis contrasted markedly with its failure to suppress tumors at other sites such as nasal sinuses, trachea, esophagus, and fore-stomach.