Sj. Culp et al., BIPHASIC REMOVAL OF DNA ADDUCTS IN A REPETITIVE DNA-SEQUENCE AFTER DIETARY ADMINISTRATION OF 2-ACETYLAMINOFLUORENE, Environmental health perspectives, 99, 1993, pp. 273-275
Dietary administration of the hepatocarcinogen 2-acetylaminofluorene (
2-AAF) to rats results in the formation of a major hepatic DNA adduct,
N-(deoxyguanosin-8-yl)-2-aminofluorene (dG-C8-AF). In liver DNA, dG-C
8-AF reaches steady-state conditions after approximately 2 weeks of fe
eding and is removed in a biphasic manner. In these experiments, we ha
ve quantified adduct concentrations in a 370 base-pair repetitive DNA
fragment to determine if the adduct levels and kinetics of adduct remo
val were similar to those found in total genomic DNA. Male F344 rats w
ere fed 0.02% 2-AAF for 28 days and were sacrificed at intermittent ti
mes up to 56 days after being returned to the control diet. Hepatic DN
A adduct levels were measured by P-32-postlabeling or radioimmunoassay
(RIA) in total genomic DNA and in a 370 base-pair fragment obtained b
y digesting genomic DNA with Hind III. Biphasic removal of dG-C8-AF, w
hich composed about 90% of the total adducts measured, was observed in
total genomic DNA, with comparable rate constants being detected by b
oth P-32-postlabeling and RIA. P-32-Postlabeling also showed analogous
biphasic removal of dG-C8-AF in the 370 base-pair fragment. A second
adduct, 3-(deoxyguanosin-N2-yl)-2-AAF (dG-N2-AAF), which accounted for
about 10% of the total adducts measured, showed similar biphasic remo
val kinetics in the total genomic DNA and the 370 base-pair fragment;
however, as compared to dG-C8-AF, little removal of dG-N2-AAF was obse
rved during the slow phase.