Specificity of certain biochemical derangements in hepatocarcinogenesis.

Earlier work on acid-soluble nucleotides and other liver constituents as affected by azo-dye carcinogenesis has now been extended, with trial of ethionine (weakly carcinogenic) and of α-naphthylisothiocyanate (noncarcinogenic). The effects of ethionine feeding on whole-tissue nucleotide levels were not dramatic, and were generally dissimilar to those produced by azo-dye feeding. However a fall in some or all of the purine nucleotides can still be regarded as a feature of hepatocarcinogenesis.A fall in mitochondrial nucleotides, as previously found in azo-dye experiments, likewise occurs with ethionine feeding, but also with α-naphthylisothiocyanate. It is suggested that the latter warrants testing as a co-carcinogen. Unlike azo-dyes, ethionine is without adverse effect on the yield of protein in cytoplasmic particles and (in common with α-naphthylisothiocyanate) it raises the yield of RNA in the supernatant fraction.In liver from ethionine-fed rats and in ethionine-induced hepatomas, the activity of enzymes concerned in UMP synthesis showed a rise more striking than that found with azo-dyes.