DNA ADDUCT FORMATION AND T-LYMPHOCYTE MUTATION-INDUCTION IN F344 RATSIMPLANTED WITH TUMORIGENIC DOSES OF 1,6-DINITROPYRENE

Diesel emissions are known to induce tumors in experimental animals an d are suspected of being carcinogenic in humans. Of the compounds asso ciated with diesel exhaust, 1,6-dinitropyrene is a particularly potent mutagen and carcinogen. In these experiments, we have investigated th e use of DNA adducts and T-lymphocyte mutations of 1,6-dinitropyrene a s biomarkers for exposure to diesel emissions. 1,6-Dinitropyrene (0-15 0 mu g) was applied directly to the lungs of male F344 rats according to a protocol known to induce lung tumors. In target (lung) and surrog ate (liver, WBC, and spleen lymphocytes) tissues, one major DNA adduct , N-(deoxyguanosin-8-yl)-1-amino-6-nitropyrene, was detected by HPLC a nd/or P-32-postlabeling analyses. The levels of this adduct reached a maximum 1-7 days following treatment and decreased to 13-50% of the pe ak values by 28 days after dosing. In the lung, a 2-fold increase in d ose resulted in a 2-fold increase in DNA binding up to the 30-mu g dos e; in the liver the same relationship was observed up to 10 mu g 1,6-d initropyrene. At higher doses, the extent of adduct formation still in creased, but the rate was much lower than that occurring at lower dose s. A limiting dilution clonal assay was used to measure mutation induc tion at the hypoxanthine-guanine phosphoribosyltranferase locus in spl een T lymphocytes. Following treatment, the mutant frequency increased until 21 weeks, remained constant until week 40, and then began to de crease. Mutant induction was dose related, with the increase in mutant frequency being significant at doses greater than or equal to 1 mu g 1,6-dinitropyrene. These data indicate that 1,6-dinitropyrene, a const ituent of diesel emissions, is metabolically activated by nitroreducti on to give DNA adducts in target and surrogate tissues. They further s uggest that T-lymphocyte mutations may be a more sensitive and longer- lived biomarker than DNA adducts for assessing previous exposures to n itropolycyclic aromatic hydrocarbons.