Abstract
The accumulation of 3-methylindole (3MI) in uncastrated male pigs (boars) is a major cause of boar taint, which negatively affects the quality of meat from the animal. Previously, CYP2E1 and CYP2A have been identified as cytochrome P450 (P450) isoforms involved in the metabolism of 3MI using porcine liver microsomes. This study further examines the role of these isoforms in the metabolism of 3MI using a primary porcine hepatocyte model by examining metabolic profiles of 3MI after incubation with P450 inhibitors. Incubation of hepatocytes with 4-methylpyrazole resulted in a selective inhibition of CYP2E1 activity as determined by p-nitrophenol hydroxylase activity and an associated significant decrease in the production of the 3MI metabolites 3-hydroxy-3-methyloxindole and 3-methyloxindole. Furthermore, inhibition of CYP2A, as assayed by coumarin 7-hydroxylase activity, using 8-methoxypsoralen and diethyldithiocarbamate was not associated with any further significant inhibition of the production of 3MI metabolites. Treatment with general P450 inhibitors resulted in further decreases in CYP2E1 activity and a more dramatic decrease in the production of 3MI metabolites, suggesting that additional P450s may be involved in the phase 1 metabolism of 3-methylindole. In conclusion, CYP2E1 activity levels are more important than CYP2A activity levels for the metabolism of 3-methylindole in isolated pig hepatocytes.
Footnotes
-
This work was supported by funding from the Ontario Ministry of Agriculture and Food and the Natural Sciences and Engineering Research Council of Canada.
-
Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
-
doi:10.1124/dmd.105.008128.
-
ABBREVIATIONS: 3MI, 3-methylindole; P450, cytochrome P450; 8-MOP, 8-methyoxypsoralen; 4MP, 4-methylpyrazole; DDTC, diethyldithiocarbamate; KCZ, ketoconazole; ABT, 1-aminobenzotriazole; 2AAP, 2-aminoacetophenone; 3MOI, 3-methyloxindole; HMOI, 3-hydroxy-3-methyloxindole; PNP, p-nitrophenol; HPLC, high-performance liquid chromatography; PNC, p-nitrocatechol; COH, coumarin 7-hydroxylase; 5-OH-3MI, 5-hydroxy-3-methylindole; 6-HO-3MI, 6-hydroxy-3-methylindole; SULT, sulfotransferase.
- Received October 31, 2005.
- Accepted February 15, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
DMD articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|