Prevention of rectal cancer induced by N-nitrosobis(2-oxopropyl)-amine by exogenous testosterone in MRC rats

Rectal carcinogenicity of N-nitrosobis(2-oxopropyl)amine (BOP)in male MRC Wistar rats was shown to be inhibited by exogenoustestosterone (T) when the hormone was given during, but notafter, administration of the carcinogen. This effect was independentof the dose and frequency of BOP, which was given either weeklyfor 20 weeks orally or daily for 3 days subcutaneously. Since,except for prostatic cancer, the incidence and the patternsof other BOP-induced tumors were not altered by T, this hormoneseems to play a specific role in the rectal carcinogenesis ofBOP.