Protective action of stock diets against the cancer-inducing action of 2-acetylaminofluorene in rats.

INTRODUCTION Investigations in this laboratory on the carcino genic action of 2-acetylaminofluorene have re vealed that the type of diet fed with the carcinogen can influence the incidence and types of tumors in duced in rats. Female rats of the Alabama Experi ment Station (AES) strain uniformly developed mammary tumors in about 4 months when they were fed this carcinogen on a semi-purified diet (7). Varying the riboflavin content of the same diet failed to influence mammary tumor induction, but supplements of teropterin or a synthetic detergent slightly enhanced mammary tumor formation (8). High levels of dietary protein inhibited mammary tumor formation (6). When rats were fed semi-purified or purified diets that were low in fat, the induction of mam mary tumors was almost completely inhibited, and tumors in the orbital cavity appeared rather fre quently (SO per cent incidence) (9). In the same study, it was also noted that caloric intake has an important bearing on the induction of mammary tumors. Female rats that would be expected to de velop mammary tumors in 90-100 per cent of the cases under a condition of adequate food intake de veloped this type of tumor in only about 50 per cent of cases under a condition of low food intake. These results thus suggest that the type of diet and the amount of diet fed to rats can have a marked in fluence on 2-acetylaminofluorene carcinogenesis. The present experiments were conducted to de termine the carcinogenicity of 2-acetylamino fluorene when it was fed in diets of natural food stuffs—i.e., adequate stock diets or modifications of such diets.