The binding of 14C-labelled acetylaminofluorene to nuclear proteins and DNA

The covalent binding of acetylaminofluorene (AAF) to rat liver nuclear protein fractions and DNA has been examined after 2 doses of 14C-labelled carcinogen (100 micronCi intraperitoneally) given at 24-h intervals. Most of the AAF (approx. 80%) was bound to the NHP which had the highest specific activity, relatively small amounts were bound to histones, residual proteins and DNA. After 2 weeks the label was more evenly distributed but little remained bound to the DNA. Pre-feeding rats with phenobarbitone (1 mg/ml in drinking water) reduced binding in all fractions. Pre-feeding rats with sodium sulphate (1 mg/ml in drinking water) also slightly lowered the binding to all fractions. Isoelectric focusing analysis (in polyacrylamide gels) of the NHP showed a complex binding pattern with no one component predominantly labelled, variations in the pattern were found after feeding sulphate and phenobarbitone. Normal histone components in the histone fraction (acid extract) contained only 25% of the labelled carcinogen present.