GENOTOXIC EFFECTS OF CYCLOPENTA-FUSED POLYCYCLIC AROMATIC-HYDROCARBONS IN DIFFERENT TYPES OF ISOLATED RAT LUNG-CELLS

The genotoxic effects of the environmental contaminants benz[j]aceanth rylene (B[j]A), benz[I]aceanthrylene (B[l]A) and benzo[a]pyrene (B[a]P ), and the metabolism of radiolabelled B[j]A, were studied using rat l ung microsomes and various types of isolated rat lung cells from contr ol and Aroclor 1254 (PCB) treated animals. All three compounds (10 or 20 mu g/plate) resulted in low but detectable, levels of His(+) revert ants in the Salmonella assay when plated with control lung microsomes. The two cyclopenta polycyclic aromatic hydrocarbons (CP-PAH) B[j]A an d B[l]A, gave increased levels of revertants when plated with microsom es from PCB-treated animals. Clara cells, type 2 cells and alveolar ma crophages isolated from control rats were exposed to B[j]A, B[l]A or B [a]P (30 mu g/ml, 1 h), but neither of the cell types showed any DNA d amage when measured by alkaline filter elution. However, both B[j]A an d B[l]A (30 mu g/ml, 2 h) caused DNA adducts in all three cell types, measured by the P-32-post-labelling technique, whereas no B[a]P adduct s were detected (30 mu g/ml, 2 h). The total DNA adduct levels in Clar a cells, 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/mu g DNA, respectively , whereas the total levels in cells exposed to B[l]A were 0.140 +/- 0. 070, 0.140 +/- 0.030 and 0.220 +/- 0.080 fmol/mu g DNA, respectively C ells exposed to B[j]A revealed only one adduct which corresponds with the B[j]A-1,2-oxide DNA adduct. Judged from high performance liquid ch romatography (HPLC) analysis using radiolabelled B[j]A (30 mu g/ ml, 3 0 min), the major metabolite formed in control microsomes was B[j]A-1, 2-diol. Thus, oxidation at the cyclopenta ring appears to be the most important activation pathway for B[j]A with control rat lung cells. Ex posure of lung cells to CP-PAH (30 mu g/ml, 2 h) isolated from PCB pre treated rats resulted in slightly increased DNA adduct levels in Clara cells and macrophages when compared to cells isolated from control ra ts. Furthermore, the adduct pattern had shifted, and no apparent B[j]A -1,2-oxide adduct could be detected on the thin layer chromatography ( TLC) plate. In contrast, the major metabolite formed with microsomes f rom PCB-treated animals was still the B[j]A-1,2-diol.