3-Methylcholanthrene-inducible binding of aromatic hydrocarbons to DNA in purified rat liver nuclei

Purified rat liver nuclei contain enzymes capable of activating polycyclic aromatic hydrocarbons which can then bind to nuclear DNA. This has been demonstrated by incubating nuclei with [¹⁴C] hydrocarbon and purifying the nuclear DNA containing bound hydrocarbon. Intraperitoneal injection of the rats with 3-methylcholanthrene twenty-four hours before livers were removed raised the level of hydrocarbon binding to nuclear DNA four-fold. Omission of reduced nicotinamide adenine dinucleotide phosphate from incubation mixtures caused a four-fold decrease in the ability of 3-methylcholanthrene induced nuclei to bind hydrocarbon to nuclear DNA. The most potent carcinogens in a series of seven hydrocarbons displayed a relatively higher extent of binding to nuclear DNA. The data suggest that nuclear aryl hydroxylases effect covalent binding of hydrocarbons to DNA and presumably initiate the cancer process.