The Levels of Carcinogenic Azo Dyes in the Livers of Rats Fed Various Diets Containing p-Dimethylaminoazobenzene Relationship to the Formation of Hepatomas*

Variations in the composition of the diet influence the rate of appearance of liver tumors in rats fed certain azo dyes. The effective dietary factors and possible mechanisms involved have been reviewed by Rusch, Baumann, Miller, and Kline (14); as yet no generally accepted explanation has been advanced either for the mode of carcinogenic action or for the means by which diet affects it. It has been shown that the rate of appearance of tumors of the skin or subcutaneous tissues, induced by carcinogenic hydrocarbons, is directly dependent on the dosage of carcinogen applied. Furthermore, there is evidence that the same relationship may be valid for the induction of hepatomas by means of azo dyes. I t may be that variations in the composition of the diet increase or decrease the rate of appearance of hepatomas by increasing or decreasing the level of azo dyes in the liver. Since the azo dyes are fat soluble, one way in which diets might produce differences in dye levels in the liver is through their effect upon the lipid content of the liver. Any diet tending to increase liver lipids might lead to high concentration of azo dyes in the liver, and in this way augment the formation of hepatomas. Consideration of the various dietary conditions known to affect the formation of induced hepatomas suggests that at least some of the diets augmenting tumor formation would tend