Alkylation of rat serum proteins by dimethylnitrosamine and acetylaminofluorene.

The labelling of rat serum proteins was studied after i.p. injections of radioactive dimethylnitrosamine (DMN) or acetylaminofluorene (AAF). Protein-bound radioactivity decayed with an apparent half-life of 49 h and 35 h after DMN and AAF treatment, respectively. Methylated amino acid residues were indentified from DMN-treated animals using thin-layer chromatography of the serum protein hydrolysates. The main methylation products were shown to be S-methylcysteine and 1-methylhistidine. The possibilities of monitoring carcinogen and mutagen exposure by analysing the alkylation of serum proteins are discussed.