Abstract

When liver cytosol prepared from rats administered [14C]3'-methyl-N,N-dimethyl-4-aminoazobenzene was subjected to Sephadex gel chromatography, four peaks (I-IV) of radioactivity containing proteins and one peak (V) of radioactivity devoid of protein were obtained. Forty to fifty-five per cent of the radioactivity in the protein peaks was butanol-extractable. When the protein peaks were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis, over 90% of the radioactivity was separated from the proteins, indicating lack of covalent binding. Several differences in the metabolite patterns were seen when the butanol-extractable metabolites from the five chromatographic peaks were analyzed by TLC. When pooled fractions of the peaks were incubated with isolated rat liver nuclei, only radioactivity associated with peak II was translocated into the nucleus. Translocation was time- and temperature-dependent and was maximal at 40 min at 37 degrees C. Only 10 to 12% of the radioactivity associated with peak II could be translocated even in the presence of an excess of nuclei, indicating that specific protein metabolite adduct(s) present in this fraction is/are translocated. Five per cent of translocated radioactivity was irreversibly bound to DNA, 3% to RNA, 67% to non-histone proteins, and 7.5% to histones; the remaining was not associated with any of these macromolecules.