Microsome-dependent methylation of erythrocyte proteins by dimethylnitrosamine

The precarcinogen, N-[methyl-14C]dimethylnitrosamine, rat liver microsomes and NADPH were incubated in the presence of intact human erythrocytes. Uptake of radioactivity into erythrocytes was time-dependent and analysis of an acid hydrolysate of the erythrocyte proteins showed several radioactive peaks which were identified as 3-N-methyl- and 1-N-methyl-histidine, S-methyl-cysteine. Since no binding occurs in the absence of microsomes, the alkylating species from dimethylnitrosamine metabolism can clearly penetrate the erythrocyte plasma membrane.