METABOLISM AND ACTIVATION OF CYCLOPENTA POLYCYCLIC AROMATIC-HYDROCARBONS IN ISOLATED HUMAN-LYMPHOCYTES, HL-60 CELLS AND EXPOSED RATS

The metabolism of radiolabelled benz(j)aceanthrylene (B(j)A) was studi ed in suspensions of isolated human peripheral mononuclear blood cells (lymphocytes), using high performance liquid chromatography (HPLC). T he only known metabolite found after 24 h exposure to 30 mu g/ml (120 mu M) B(j)A, was B(j)A-1,2-dihydrodiol, representing approximately 35% of the total metabolites formed. B(j)A, benz(1)aceanthrylene (B(1)A) and benzo(a)pyrene (B(a)P) all caused DNA adducts in human lymphocytes , as well as in the human promyelocytic cell line HL-60 cells, as meas ured by the P-32-postlabelling technique (30 mu g/ml, 24 h). The total DNA adduct levels in human lymphocytes exposed to B(j)A, B(1)A or B(a )P were 0.13 +/- 0.03, 1.10 +/- 0.62 and 0.37 +/- 0.10 fmol/mu g DNA, respectively, and similar levels were obtained in HL-60 cells (0.18 +/ - 0.14, 0.97 +/- 0.35 and 0.29 +/- 0.17 fmol/mu g DNA, respectively). For each compound, the human lymphocytes and HL-60 cells in addition s howed similar DNA adduct patterns. Cells exposed to B(j)A revealed onl y one DNA adduct, which, judged by its TLC properties, resulted from B (j)A-1,2-epoxide. As measured by the alkaline filter elution technique , only low levels of single strand DNA breaks (SSB) were observed in b oth human lymphocytes and HL-60 cells after exposure to B(j)A, B(I)A o r B(a)P (24 h, 30 mu g/ml). By adding cytosine-1-beta-D-arabino-furano side (Are C) and hydroxyurea (HU) 1 h prior to analysis to prevent str and break rejoining, some increase in SSB (2-3 times) was observed in the lymphocytes. Go-incubation of human lymphocytes with liver microso mes from PCB-treated rats for 1 h and exposure to B(j)A or B(1)A, incr eased the DNA adduct levels in the lymphocytes to 12.3 and 37.8 fmol/m u g DNA, respectively. A large increase in SSB was also observed, wher eas no such increase was observed after co-incubation with human liver microsomes. In vivo exposure of rats to 30 mg/kg B(j)A (i.p.) for 24 h revealed one major DNA adduct in lymphocytes and lung tissue (only o ne of three rats showed an adduct in liver tissue), apparently resulti ng from B(j)A-1,2-epoxide. The total DNA adduct level in the lymphocyt es was 0.09 fmol/mu g DNA, and in lung tissue between 0.10 and 0.62 fm ol/mu g DNA. Overall, the present data suggests that oxidation at the cyclopenta-ring is an important activation pathway for B(j)A in rats a s well as in humans. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.