The influence of dietary casein level on tumor induction with 2-acetylaminofluorene.

INTRODUCTION The present experiments were conducted to de termine the carcinogenicity of 2-acetylaminofluorene when it was fed in partially purified diets that varied in casein level between 9 and 60 per cent. Studies involving this broad range of dietary protein level have not been reported previously with this carcinogen. Harris (7) concluded that variations in dietary protein level had no appreciable effect on the pro duction of liver tumors with 2-acetylaminofluorene in rats. Purified diets containing 13 and 20 per cent of casein were employed. Morris and associates (10) found that rats developed more tumors when purified diets containing 18-24 per cent of casein were used than when the diet contained 12 per cent of casein. In these studies, it was noted that dietary pro tein levels in the range used by the above investi gators had no influence on tumor induction by 2-acetylaminofluorene. However, it was observed that diets containing 40 or 60 per cent of casein had a definite protective effect against the induc tion of mammary tumors and possibly other types of tumors.