RT Journal Article
SR Electronic
T1 Bupropion Hydroxylation as a Selective Marker of Rat CYP2B1 Catalytic Activity
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 32
OP 38
DO 10.1124/dmd.111.041368
VO 40
IS 1
A1 Dumrongsak Pekthong
A1 Coraline Desbans
A1 Hélène Martin
A1 Lysiane Richert
YR 2012
UL http://dmd.aspetjournals.org/content/40/1/32.abstract
AB Benzyloxyresorufin-O-dealkylation (BROD) is usually used as a marker of cytochrome P450 (P450) 2B1 in rat. However, some reports show that CYP1A2 is also highly implicated. The purpose of the present study was to establish bupropion (BUP) hydroxylation, but not BROD, as a selective in vitro marker of CYP2B1 catalytic activity. IC50 for BROD and BUP hydroxylation were equivalent (40.8 ± 4.6 and 41.8 ± 3.4 μM, respectively) when using liver microsomes from β-naphthoflavone-pretreated rats in the presence of metyrapone (CYP2B1 inhibitor). When using the same microsomes in the presence of CYP1A1/2-selective inhibitor α-naphthoflavone, we found an IC50 of 2.5 × 10−3 ± 0.8 × 10−3 μM for BROD and >100 μM for BUP hydroxylation. These results suggest that CYP2B1 is similarly involved in both activities, whereas CYP1A2 is involved in BROD activity but not in BUP hydroxylation. BUP hydroxylation was assessed in microsomes from baculovirus-infected insect cells coexpressing NADPH-P450 oxidoreductase, and 14 rat P450s and kinetic parameters (Km and Vmax) were determined. BUP hydroxylation was predominantly catalyzed by CYP2B1 (75% of total hydroxybupropion formation), low activity was detected with CYP2E1 and CYP2C11 (10.9 and 8.7% of total hydroxybupropion, respectively), and activity was almost undetectable with the other P450 isoforms at saturating substrate concentrations (2500 μM), thereby validating the use of BUP as a diagnostic in vitro marker of CYP2B1 catalytic activity in rat.