Inter-laboratory evaluation of the response of primary human hepatocyte cultures to model CYP inducers - a European Centre for Validation of Alternative Methods (ECVAM) - funded pre-validation study.

The aim of the current work was to harmonise protocols between three laboratories by performing independent isolations and cultures of human hepatocytes and to assess their responses to prototypical cytochrome P450 (CYP) enzyme inducers, β-naphthoflavone (BNF), rifampicin (RIF) or phenobarbital (PB). The magnitudes of the induction responses were CYP and donor-dependent but there was a good reproducibility between laboratories. CYP1A2 activity was evident in all cultures treated with BNF but not RIF or PB. Likewise, CYP3A4/5 activity was induced to the same extent by RIF and PB, while BNF did not affect this CYP in any of the cultures tested. All three compounds caused a concentration-dependent increase in CYP2B6 in cultures from 2 of the 3 laboratories and the response to PB was at least twice that of the other two inducers. In conclusion, the harmonised protocols used to study the response of primary cultures of human hepatocytes to prototypical inducers are transferable, reproducible within a given laboratory and between laboratories. The results obtained will support setting up a definitive validation study of the harmonised protocols.