Effects of benzo(a)pyrenf and tetrachlorodibenzo(p) dioxin on fetal dolphin kidney cells: Inhibition of proliferation and initiation of DNA damage

Dolphin kidney cells (CDK) were exposed to benzo(a)pyrene (BaP) in the presence or absence of 2,3,7,8-tetrachlorodibenzo(p)dioxin (TCDD), a cytochrome P450-inducing agent, and/or α-naphthoflavone (α NF), an inhibitor of cytochrome P450 induction. BaP inhibited mitosis in CDK cells in a dose-dependent manner. TCDD, while inhibiting cell proliferation, did not show a strict dose-dependent mode of action. BaP inhibition of mitosis was decreased by αNF, which also decreased the inhibitory effects of TCDD on CDK proliferation. BaP treatment initiated both 3H-thymidine incorporation and the increased alkali lability of DNA functions of the initiation of excision repair. Cells pre-treated with TCDD and then exposed to BaP exhibited increased BaP-DNA adduct levels and increased DNA excision repair. These data indicate that dolphin cells metabolized BaP as a function of cytochrome P450-associated activities, that BaP metabolites covalently bound to cellular DNA and initiated excision repair. Inhibition of the cytochrome P450-mediated metabolism of BaP decreased the BaP-associated inhibition of mitosis in dolphin cells.