Enhancement by urine of urinary bladder carcinogenesis.

The role of urine as a tumor-enhancing agent in urinary bladder carcinogenesis was investigated by using the heterotopically transplanted rat urinary bladder. Bladders removed from rats initiated with the carcinogen N-butyl-N-(4-hydroxybutyl)nitrosamine in drinking water for 4 or 10 weeks were heterotransplanted to syngeneic rats. These heterotopically transplanted bladders receiving repeated instillations of normal rat urine subsequent to transplantation had a higher incidence of carcinoma than did those receiving 0.9% NaCl solution. These results suggest that normal urine may contain tumor promoter(s).