The uniform carcinogenic action of alkylnitrosoureas in Syrian hamsters

The carcinogenic effects of a number of alkylnitrosoureas in Syrian golden hamsters have been compared by administering them by gavage as solutions in corn oil/ethyl acetate. The compounds were methyl-, ethyl-, 2-hydroxyethyl-, 2-oxopropyl-, and 2-phenylethylnitrosourea and the dialkylnitrosoureas dimethyl- and diethylnitrosourea, ethylnitrosohydroxyethylurea, ethylnitroso-2-oxopropylurea, 2-oxopropylnitrosochloroethylurea, and hydroxyethylnitrosoethylurea. All were given at approximately equimolar doses and, in most cases, to male and female hamsters. Most of the hamsters died with tumors associated with the treatments. Methylnitrosourea, ethylnitrosourea, and hydroxyethylnitrosourea, but not oxopropylnitrosourea, gave rise to a high incidence of tumors of the forestomach, while the dialkylnitrosoureas produced smaller numbers of forestomach tumors. All of the alkylnitrosoureas induced hemangiosarcomas of the spleen, which was the most common tumor produced by these carcinogens. Tumors of other types were uncommon, except that ethylnitrosourea and ethylnitrosohydroxyethylurea induced tumors of the cervix in about half of the animals and ethylnitrosooxopropylurea induced some nervous system tumors. The small number of common target organs of alkylnitrosoureas in hamsters contrasted sharply with the broad spectrum of tumors they induced in rats, depending on the nature of the alkyl groups, and with a quite different order of potency in the latter species.