Figure 3.
E2 inhibits antiestrogen-mediated induction of NAD(P)H:quinone oxidoreductase enzyme activity in MCF-7 cells. MCF-7 cells were treated with different concentrations of TOT and ICI or with 10−5 M TBHQ with or without E2 at the concentrations indicated. Cells were harvested after 4 days of treatment. Cytosolic extracts were assayed for QR activity as described. A similar extent of inhibition of QR activity by TOT and ICI was observed with 10−6 M and 10−7 M E2, and therefore only 10−6 M and 10−8 M E2 data are shown. Values are the means ± SE from three separate experiments.