USPHS and E-73 from the American Cancer Society, and by the fol

The various soluble liver protein-carcinogen conjugates produced in vivo by two hepatocarcinogens have been resolved and analyzed according to molecular size. In addition, the molecular sizes of the principal soluble conjugates of three types of carcinogens have been compared in order to deduce whether they originate from a common or similar target pro tein. Adult male rats were fed the liver carcinogen 3'-methyl-4dimethylaminoazobenzene for 18 to 21 days. Gel ifitration of the soluble proteins of perfused livers revealed the presence of five species of azoproteins: The principal conjugate had 62% of the soluble protein-bound dyes, belonged to the 55 class of macromolecules, and was of 60,000 to 80,000 molecular weight. This azoprotein is identical to the previously characterized principal charge species, slow h2 . A minor azo protein (19%) was a 45 macromolecule (30,000 to 40,000) and is apparently the basic h3 conjugate previously separated on the basis of charge. Small amounts of azo dyes (“@†̃5%) were