Genotoxic effects of cyclopenta-fused polycyclic aromatic hydrocarbons in different types of isolated rat lung cells

The genotoxic effects of the environmental contaminantsbenz[j]aceanthrylene (B[j]A), benz[l]aceanthrylene (B[l]A) andbenzo[a]pyrene (B[a]P), and the metabolism of radiolabelled B[j]A, werestudied using rat lung microsomes and various types of isolated rat lungcells from control and Aroclor 1254 (PCB) treated animals. All threecompounds (10 or 20 microg/plate) resulted in low, but detectable, levelsof His+ revertants in the Salmonella assay when plated with control lungmicrosomes. The two cyclopenta polycyclic aromatic hydrocarbons (CP-PAH)B[j]A and B[l]A, gave increased levels of revertants when plated withmicrosomes from PCB-treated animals. Clara cells, type 2 cells and alveolarmacrophages isolated from control rats were exposed to B[j]A, B[l]A orB[a]P (30 microg/ml, 1 h), but neither of the cell types showed any DNAdamage when measured by alkaline filter elution. However, both B[j]A andB[l]A (30 microg/ml, 2 h) caused DNA adducts in all three cell types,measured by the 32P-post- labelling technique, whereas no B[a]P adductswere detected (30 microg/ml, 2 h). The total DNA adduct levels in Claracells, type 2 cells and macrophages exposed to B[j]A were 0.085 +/- 0.033,0.053 +/- 0.001 and 0.170 +/- 0.030 fmol/microg DNA, respectively, whereasthe total levels in cells exposed to B[l]A were 0.140 +/- 0.070, 0.140 +/-0.030 and 0.220 +/- 0.080 fmol/microg DNA, respectively. Cells exposed toB[j]A revealed only one adduct which corresponds with the B[j]A-1,2- oxideDNA adduct. Judged from high performance liquid chromatography (HPLC)analysis using radiolabelled B[j]A (30 microg/ml, 30 min), the majormetabolite formed in control microsomes was B[j]A-1,2-diol. Thus, oxidationat the cyclopenta ring appears to be the most important activation pathwayfor B[j]A with control rat lung cells. Exposure of lung cells to CP-PAH (30microg/ml, 2 h) isolated from PCB pretreated rats resulted in slightlyincreased DNA adduct levels in Clara cells and macrophages when compared tocells isolated from control rats. Furthermore, the adduct pattern hadshifted, and no apparent B[j]A-1,2- oxide adduct could be detected on thethin layer chromatography (TLC) plate. In contrast, the major metaboliteformed with microsomes from PCB-treated animals was still theB[j]A-1,2-diol.