Effect of phenacetin and caffeine on the urinary bladder of rats treated with N-butyl-N-(4-hydroxybutyl)nitrosamine.

The effect of phenacetin and caffeine on urinary bladder carcinogenesis in rats treated with N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) was examined. Animals were given a high or low dose of BBN for 4 weeks and then phenacetin or caffeine was administered for 30 or 32 weeks, respectively. All the animals were examined histologically after 36 experimental weeks. The incidence of papillary or nodular hyperplasia, papilloma, and cancer of the urinary bladder was significantly higher in the groups treated with BBN and then with phenacetin than in those treated with BBN alone, especially with a high dose of BBN. Simple hyperplasia and papillary or nodular hyperplasia developed in the urinary bladder of rats treated with phenacetin alone. Papillary proliferative growth of the renal pelvis was seen in one rat treated with a low dose of BBN and phenacetin. Treatment with caffeine after BBN had no enhancing effect and caffeine alone caused no remarkable changes.