| Assay Method Information | |
| | Inhibition of Cytochrome P450 Enzyme |
| Description: | Solutions of each test compound were separately prepared at concentrations of 20000, 6000, 2000, 600, 200, and 60 μM by serial dilution with DMSO:MeCN (50:50 v/v). The individual test compound solutions were then diluted 20-fold with DMSO:MeCN:deionized water (5:5:180 v/v/v) to concentrations of 1000, 300, 100, 30, 10, and 3 μM. Mixtures of isozyme inhibitors (sulfaphenazole, tranylcypromine, and ketoconazole as specific inhibitors of isozymes 2C9, 2C19, and 3A4, respectively) were prepared containing each inhibitor at concentrations of 6000, 2000, 600, 200, 60, 20, 6, and 2 μM by serial dilution with DMSO:CH3CN (50:50 v/v). The mixed inhibitor solutions were then diluted 20-fold with DMSO: CH3CN:deionized water (5:5:180 v/v/v) to concentrations of 300, 100, 30, 10, 3, 1, 0.3, and 0.1 μM. The percent of organic solvent attributable to the test compound or inhibitor mixture in the final reaction mixture was 2% v/v.Pooled human liver microsome suspension (20 mg/mL) was diluted with phosphate buffer to obtain a 5 mg/mL suspension. A solution of NADPH was prepared in phosphate buffer at a concentration of 5 mM. Separate stock solutions of each substrate were prepared in DMSO:MeCN (50:50 v/v), mixed, and diluted in phosphate buffer to obtain a single solution containing each substrate at five times its experimentally determined Km concentration. The percent of organic solvent attributable to substrate mixture in the final reaction mixture was 1% v/v.Substrate solution and microsome suspension were combined in a 1:1 volume ratio, mixed, and distributed to reaction wells of a PCR plate. Individual test compound or combined inhibitor solutions at each concentration were added to the wells and mixed by repetitive aspirate-dispense cycles. For active controls, blank phosphate buffer solution was added in place of test compound solution. Reaction mixtures were allowed to equilibrate at 37° C. for approximately two minutes before adding NADPH solution to initiate reaction, followed by pipette mixing of reaction mixture. Ten minutes after addition of NADPH, the reaction mixtures were quenched with cold acetonitrile. |
| Affinity data for this assay | |
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