Effects of sex hormones on development of urinary bladder tumours in rats induced by N-butyl-N-(4-hydroxybutyl) nitrosamine.

Male and female Wistar strain rats were given 0.05% N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) in their drinking water for 6 weeks and then water without BBN for 18 weeks. Diethylstilbestrol and testosterone were implanted subcutaneously into both intact and gonadectomised animals before or after treatment with BBN to evaluate their effects on the development of bladder tumours. Diethylstilboestrol reduced the incidence of bladder tumours significantly in male rats. The incidence was higher in female rats after spaying and administration of testosterone after BBN treatment, than in the intact female. These results suggest that diethylstilboestrol inhibits carcinogenesis of the urinary bladder induced by BBN and growth of bladder tumours induced by BBN, in male rats. On the other hand, testosterone seems to stimulate the growth of bladder tumours induced by BBN in female rats.