Figure 5.

NQO1 and b₅R levels. (A) Cytosolic fractions were obtained from wild-type (Wt) or Nrf2−/− murine embryonic fibroblasts (MEFs) obtained from the indicated passages and then assayed for NQO1 enzymatic activity. A significant increase of NQO1 activity was observed in Wt MEFs from Passages 10 to 15, at the beginning of cellular immortalization. On the other hand, as expected, NQO1 activity remained low in Nrf2−/− cells at any passage. Data are means ± SDs of measures taken in triplicate. (B) Membranous fractions were obtained from Wt or Nrf2−/− MEFs obtained from the indicated passages. Proteins were separated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and blotted onto nitrocellulose. Blots were then probed for b₅R with a specific antiserum. The immunostained 34-kDa band was quantified with Quantity one software (Bio-Rad), and the results normalized to the density of the corresponding lane stained with Ponceau S. Results from a representative blot are shown.