The role of testosterone in the nasal cavity tumors induced by N-nitrosobis(2-oxopropyl)amine in rats.

In a previous study in rats we have shown that castration prior to weekly administration of N-nitrosobis(2-oxopropyl)amine (BOP) prevents induction of nasal and paranasal cavity (NPNC) tumors, indicating androgen dependency of these neoplasms. To investigate the possible inhibitory effect of testosterone withdrawal on the growth of NPNC tumors, in the present study rats were castrated following weekly treatment with BOP for 10, 20 or 30 weeks. This treatment did not alter the incidence, type, location, latency or multiplicity of NPNC tumors. However, simultaneous treatment of castrated rats with BOP and testosterone (T) yielded NPNC tumors in an incidence and patterns comparable to that seen in BOP-treated intact and BOP-plus-T-treated intact rats. Serological examination revealed abnormally high levels of T and 17-beta estradiol (E) in rats, which were killed immediately after 10, 20 or 30 weekly BOP administrations. The overall results suggest that the initiation but not the promotional stage of NPNC carcinogenesis is governed by androgens.