| Assay Method Information | |
| | Cytochrome P450 Isoenzyme Inhibition Assays |
| Description: | The inhibition of the conversion of a specific substrate to its metabolite is assayed at 37° C. with human liver microsomes and used to determine the inhibition of cytochrome P450 isoenzymes. For the following cytochrome P450 isoenzymes, these substrates and metabolic reactions are monitored: P450 3A4: hydroxylation of Midazolam (MDZ).The final incubation volume contains TRIS buffer (0.1 M), MgCl2 (5 mM), a certain concentration of human liver microsomes dependent on the P450 isoenzyme measured (P450 3A4: 0.1 mg/ml) and a certain concentration of the individual substrate for each isoenzyme (P450 3A4: Midazolam 5 μM).The effect of the test compound is determined at five different concentrations in duplicate (e.g. highest concentration 50 μM with subsequent serial 1:4 dilutions) or without test compound (high control). Following a short preincubation period, reactions are started with the cofactor (NADPH, 1 mM) and stopped by cooling the incubation down to 8° C. and subsequently by addition of one volume of ACN. An internal standard solution—usually the stable isotope of the formed metabolite—is added after quenching of incubations. Peak area analyte (=metabolite formed) and internal standard is determined by LC-MS/MS. |
| Affinity data for this assay | |
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