Fig. 3.

CYP2D6 repression by GW4064 is abrogated in Shp(−/−);CYP2D6 mice. Shp(+/+);CYP2D6 or Shp(−/−);CYP2D6 mice were injected with GW4064 (10 mg/kg) or vehicle (olive oil) intraperitoneally daily for 5 days (n = 5 per group). (A) CYP2D6 and Cyp8b1 mRNA expression levels were measured by using qRT-PCR and normalized by those in vehicle-treated Shp(+/+);CYP2D6 mice. (B) CYP2D6 protein expression level was measured by Western blot. The image of Western blot (right) and the quantified band intensities (CYP2D6/β-actin) (left) are shown after normalization by CYP2D6 expression in the vehicle-treated mice of the respective genotype. (C) S9 from the mice was incubated with debrisoquine (200 μM), and 4-hydroxydebrisoquine concentrations were measured by using liquid chromatography–tandem mass spectrometry. Data shown are 4-hydroxydebrisoquin production rates (in pmol/min per mg protein). Values are presented as mean ± S.E.M. (n = 5). *P < 0.05; **P < 0.01; n.s., not statistically significant.