Induction of tumors of the urinary bladder in female mice following surgical implantation of glass beads and feeding of bracken fern.

The carcinogenic effect of bracken fern (Pteris aquilina) to the urinary bladder of mice was studied. Powdered bracken fern mixed with a basic commercial diet (1:4 by weight) was fed to a group of 40 ICR strain mice for 20 weeks after the implantation of a glass bead into the bladder. A total experimental period was 70 weeks. Fifteen mice survived 40 or more weeks and 4 mice (27%) developed urinary bladder tumors. No urinary bladder tumor was found in the group of mice fed a similar bracken fern diet mixture without a glass bead in their bladder and in the control group of mice fed a normal diet after the implantation of a glass bead. The result of this experiment may indicate that there is a metabolite(s) in the urine of bracken-fed mice carcinogenic to the bladder.