Systemic and local carcinogenesis by directly acting N-nitroso compounds given to rats by intravesicular...

A number of directly acting carcinogenic N-nitroso compounds were administered to female F344 rats intravesically, to assess their ability to induce tumors locally in the urinary bladder and systemically following absorption through the bladder mucosa. The compounds were alkylnitosoureas and alkylnitrosocarbamates and could be formed by interaction of amides with bacterially produced nitrite in infected bladders. Methylnitrosourethane was very toxic: doses of 1-2 mg caused death of some rats. A total dose of 0.15 mmol of ethylnitrosourethane, which was much less toxic, was administered to each rat and almost all developed bladder tumors. Ethylnitrosourea also gave rise to bladder tumors following intravesical treatment, and induced some tumors systemically, whereas methylnitrosourea, 2-methoxyethylnitrosourea and 2-hydroxypropylnitrosourea induced bladder tumors in high incidence and few tumors systemically. Nitrosooxazolidone was quite toxic and induced few bladder tumors. The dialkylnitrosoureas were more stable and some induced more tumors systemically than the monoalkylnitrosoureas. 1,3-Dimethylnitrosourea induced no bladder tumors and 1,3-diethylnitrosourea very few, but both induced tumors systemically that were similar to those induced by gavage treatment of rats. 1-Ethyl-1-nitroso-3-hydroxyethylurea, 1-hydroxyethyl-1-nitroso-3-ethylurea and 1-(2-hydroxypropyl)-1-nitroso-3-(2-chloroethyl)-urea induced bladder tumors in a majority of rats treated intravesically; the first induced many tumors systemically. Most of the bladder tumors were transitional cell papillomas and carcinomas, but there were a few squamous cell tumors, smooth muscle tumors, sarcomas and carcinosarcomas. The effects of intravesical administration of the directly acting alkylating compounds are compared with the effects of similar doses given to rats by gavage.