The inhibition of the carcinogenicity of p-dimethyl-aminoazobenzene by certain detergents and the effect of diet on the levels of azo dyes in rat tissues.

It is well established that the rate at which liver tumors occur in rats fed p-dimethylaminoazobenzene can be altered greatly by dietary means. This subject has been reviewed through 1944 (15) and extended in more recent work (3~ 16, 17). The dietary inhibitors and accelerators that have been reported include members of the vitamin B complex, certain lipids, some sulfur-containing amino acids, at least one mineral element, and various crude natural materials. A consideration of the work of Frazer (1, 2) on the partition of olive oil between the lymphatic and portal systems of the intestine, particularly in the presence of a detergent, led us to try the effects of feeding low levels of two commercial synthetic detergents on the production of liver tumors in the rat. These substances were found to represent a new type of dietary inhibitor for p-dimethylaminoazobenzene and hence form the main subject of the present communication. Analyses of the content of basic azo dyes in the blood and livers of rats fed this dye in diets which affect its activity are also presented.