Assay Method Information

Assay Name:  Cell-Based Inhibitor Assay
Description:  CYP26A1 or CYP26B1 stably transfected HeLa cells were maintained in Minimum Essential Medium (MEM) containing 10% fetal bovine serum (FBS) and 100 μg/mL hygromycin. Exponentially growing cells were harvested by incubation in trypsin. Cells were then collected and re-plated in 48-well culture plates at 5×105 cells in 0.2 mL of culture medium containing 0.05 μCi [3H]-RA in the presence or absence of increasing concentrations of a test compound. The test compounds were diluted in dimethyl sulfoxide (DMSO) and then added in duplicate to wells at 0.01, 0.1, 1, 10 and 100 μM final concentration. As a positive control for inhibition of RA metabolism, cells were also incubated with ketoconazole at the same concentrations as above. Cells were incubated for 3 hours at 37° C. Retinoids were then extracted using the procedure of Bligh, et al., (1959), Canadian Journal of Biochemistry 37, 911-917, which was modified by using dichloromethane instead of chloroform. Each sample's water soluble radioactivity level was quantified using a β-scintillation counter (using Ecolume scintillation fluid, available from MP Biomedicals of Solon, Ohio, USA). IC50 values represented the concentration of inhibitor required to inhibit all trans-RA metabolism by 50%, and were derived from log transformed data.
Affinity data for this assay
 

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