Carcinogenic Effect of Aminoazobenzene

Abstract

SINCE Kinosita¹ first showed that rats developed malignant tumours of the liver when fed a deficient diet containing N,N-dimethyl-p-aminoazobenzene (butter-yellow), much work has been done in an attempt to elucidate the mechanism whereby this azo-dye brings about neoplastic changes in liver tissue. One aspect studied has been the metabolism of the dye itself; Stevenson, Dobriner and Rhoads² were able to isolate p-aminophenol and p-phenylenediamine, and also their N-acetylation products, from the urine of rats receiving the dye orally. Thus the azo-link is split as in the case of o-aminoazotoluene³ and other azo-compounds in the animal body. However, the absence of N,N-dimethyl-p-phenylene-diamine from fractions prepared without addition of sodium hydrosulphite suggested that complete demethylation occurs at some stage prior to the acetylation of the p-phenylenediamine. This lability of the N-methyl groups has been neatly demonstrated by Jacobi and Baumann⁴, who found butter-yellow could function like other methyl-donors in protecting young rats against kidney lesions when on a choline-free diet.