COVALENT BINDING OF 2-ACETYLAMINOFLUORENE, 2-AMINOFLUORENE, AND N-HYDROXY-2-ACETYLAMINOFLUORENE TO RAT-LIVER NUCLEAR-DNA AND PROTEIN INVIVO AND INVITRO

  • 1 January 1980
    • journal article
    • research article
    • Vol. 40  (10) , 3579-3584
Abstract
Binding of the hepatocarcinogen 2-acetylaminofluorene (AAF) and 2 metabolites, 2-aminofluorene (AF) and N-hydroxy-2-acetylaminofluorene (N-OH-AAF), to the DNA and protein of rat hepatic nuclei was examined in vitro and in a cell-free system. Three and one-half h following a single injection of each compound in equimolar amounts, DNA contained .apprx. 50% more of the compounds per mg than did protein. The amount of N-OH-AAF bound to DNA was 4 times greater than that of AAF, while AF bound in intermediate amounts. When incubated with nuclei in a cell-free system, AAF seldom bound in measurable amounts, while significant amounts of N-OH-AAF and AF bound to DNA and protein. As occurred in vivo, DNA bound more of each per mg than did protein. The amount of N-OH-AAF bound to intranuclear DNA increased 54% when an aliquot of the postmicrosomal liver fraction was added to the incubation mixture, but maximum binding of AF occurred in the absence of any other liver fraction. Two AAF metabolites, AF and N-OH-AAF, bind covalently to the DNA and protein of hepatic nuclei more readily than does AAF itself and that binding in a cell-free system parallels binding in vivo. Additional evidence suggests that rat hepatic nuclei are capable of mediating the binding of AF and N-OH-AAF to macromolecules through distinct enzyme systems. The nucleus is capable of metabolizing AF to an electrophile that can bind covalently to DNA.

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