Comparative carcinogenesis by nitrosomethylalkylamines in Syrian hamsters

Six homologous nitrosomethyl-n-alkylamines, from n-propyl (C-3) to n-octyl (C-8), were administered by gavage to groups of 12 male and 12 female Syrian golden hamsters as solutions in corn oil:ethyl acetate (2:1). The solutions of C-8 to C-4 were equimolar; nitrosomethyl-n-butylamine (C-4) and nitrosomethyl-n-propylamine (C-3) were given at a lower concentration. Treatment with 0.2 ml of solution lasted 23 to 50 wk, being stopped when several hamsters had died. Additional groups of hamsters were treated similarly with nitrosomethylaniline and nitrosomethylcyclohexylamine. Excepting hamsters given the latter, treated animals had reduced survival compared with controls. The incidence of tumors in hamsters given nitrosomethylaniline and nitrosomethylcyclohexylamine was low and occurred in the liver, lungs, and spleen. Hamsters treated with nitrosomethyl-n-propylamine and nitrosomethyl-n-butylamine suffered the greatest decrease in survival. Potency judged by this criterion decreased as the size of the molecule increased in the homologous series. Virtually all of these treated hamsters died with tumors not seen in controls. These tumors, which were common in hamsters given all of the nitrosomethyl-n-alkylamines, were in the liver, lung, forestomach, and nasal mucosa, but the incidences varied somewhat between the compounds and between sexes. Bladder tumors were seen only in hamsters given nitrosamines containing even numbers of carbon atoms in the chain, namely, nitrosomethyl-n-hexylamine and nitrosomethyl-n-octylamine.