PT  - JOURNAL ARTICLE
AU  - Dumrongsak Pekthong
AU  - Coraline Desbans
AU  - Hélène Martin
AU  - Lysiane Richert
TI  - Bupropion Hydroxylation as a Selective Marker of Rat CYP2B1 Catalytic Activity
AID  - 10.1124/dmd.111.041368
DP  - 2012 Jan 01
TA  - Drug Metabolism and Disposition
PG  - 32--38
VI  - 40
IP  - 1
4099  - http://dmd.aspetjournals.org/content/40/1/32.short
4100  - http://dmd.aspetjournals.org/content/40/1/32.full
SO  - Drug Metab Dispos2012 Jan 01; 40
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.