Description:
Purpose: High quality human hepatocytes are expensive and difficult to obtain. The purpose of the study was to detemine if immortalized human hepatocytes could be an alternative model for induction of drug metabolism enzymes and transporters. Methods: Immortalized human hepatocytes Fa2N cells were obtained from Xenotech and cultured using the medium from Xenotech. Enzyme activities CYP3A4 (formation of alpha-hydroxymidazolam), CYP2C9 (formation of 4’-hydroxydiclofenac), and CYP1A2 (formation of acetaminophen), and uptake of [3H] estradiol-17-(-glucuronide (E217G) and [3H] digoxin were measured 72 hrs after treatment of test compounds. Results: Low basal activity of CYP3A4 in Fa2N cells and 5-10-fold induction by rifampin (10 µM) were observed across passages. The treatment of rifampin increased CYP2C9 activity by 2.1 fold. These cells also responded to CYP1A2 inducers in a similar manner to fresh human hepatocytes. (-naphthoflavone (25 µM) induced CYP1A2 activity by 7 and 11-fold in Fa2N cells and fresh human hepatocytes, resepectively. In Fa2N cells, treatment with proprietary compounds X, Y and Z induced CYP1A2 activity by 2.5, 11 and 39-fold at a concentration of 1 µM, and by 7, 12 and 111-fold at a concentration of 10 µM, respectively. In fresh human hepatcoytes, compounds X, Y and Z increased CYP1A2 activity by 1.0, 4.7, 27-fold at the concentration of 1 µM and 12, 1.1, 13-fold at the concentration of 10 µM, respectively. No significant temperature-dependent uptake of E217G was observed in Fa2N cells. In contrast, digoxin uptake at 2 min was 5.6 and 1.3 (pmol/mg protein) at 37 and 4 °C, respectively. Rifampin had no significant effect on uptake of E217G and digoxin. Conclusions: Fa2N cells responded to CYP450 inducers in a similar manner as fresh human hepatocytes. Further studies will be conducted to determine if transporters can be induced in these cells.
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