Factors influencing elevation of intracellular Ca2+ in the MCF-10A human mammary epithelial cell line by carcinogenic polycyclic aromatic hydrocarbons

Carcinogenic polycyclic aromatic hydrocarbons and a halogenated aromatic hy drocarbon, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), were evaluated for t heir effects on intracellular Ca2+ in the human mammary epithelial cell lin e MCF-10A. After two 18-h incubations with MCF-10A cells, benzo[a]pyrene (B aP; 1, 3, and 10 mu M) produced a dose-dependent increase in intracellular Ca2+. 7,12-Dimethylbenz[a]anthracene increased Ca2+ at 10 mu M, whereas 3-m ethycholanthrene and TCDD did not. The Ca2+-elevating effect of BaP appeare d to be dependent on the influx of extracellular Ca2+, as addition of the C a2+ chelator EGTA to the extracellular medium prevented the increase in Ca2 + MCF-10A cells were found by polymerase chain reaction to express cytochro me P4501A and P4501B isozymes as well as the aryl hydrocarbon receptor and aryl hydrocarbon receptor nuclear translocator mRNAs associated with cytoch rome P450 induction. Certain cytochrome P450-derived metabolites, including benzo[a]pyrene-7,8-diol (BP-diol) and benzo[a]pyrene-7,8-diol-9, 10-epoxid e (BPDE), were more effective in increasing Ca2+ than was BaP. The Ca2+-ele vating effect of BP-diol was prevented by alpha-naphthoflavone, a cytochrom e P4501A and P4501B inhibitor, but not by the antioxidant N-acetylcysteine. These results suggest that cytochrome P450-dependent formation of BPDE fro m BP-diol is a major mechanism required for elevation of Ca2+ in MCF-10A ce lls. (C) 1999 Wiley-Liss, Inc.