Metabolism of 7,12-dimethylbmethylbenz(a)anthracene by macrophages and uptake of macrophage-derived metabolites by respiratory tissues in vitro.

Cultured mouse macrophages and tracheal and lung tissue each produced the same ethyl acetate-soluble derivatives of 7,12-dimethylbenz(a)anthracene (DMBA). The derivatives produced in the different cultures were indistinguishable by thin-layer chromatography and by high-pressure liquid chromatography but differed in their relative proportions. The greatest difference was seen between lungs and macrophages. The predominant metabolite produced by lungs was 8,9-dihydro-8,9-dihydroxy-7,12-dimethylbenz(a)anthracene, while macrophages produced equal quantities of both 8,9-dihydro-8,9-dihydroxy-7,12-dimethylbenz(a)anthracene and a second uncharacterized derivative, Metabolite B, at low DMBA doses (less than 0.05 microgram/ml medium) and primarily Metabolite B at higher DMBA doses (greater than 0.05 microgram/ml medium). Macrophages released the majority of the ethyl acetate-soluble metabolites that they produced into the surrounding medium. With the exception of 8,9-dihydro-8,9-dihydroxy-7,12dimethylbenz(a)anthracene, these derivatives were accumulated within tracheal and lung tissue when these organs were cocultivated with macrophages in the presence of DMBA.