Studies on the importance of microsomal epoxide hydrolase in the detoxification of arene oxides using the heterologous expression of the enzyme in mammalian cells

In order to investigate the role of the microsomal epoxide hydrolase(mEH) in the detoxification of arene oxides in the presenceof a high endogenous glutathione S-transferase (GST) activity—asituation found in several organs—we expressed the ratmEH cDNA in BHK21 Syrian hamster cells. These cells have highGST activities but contain an extremely low endogenous mEH enzymeactivity. We obtained several cell clones which expressed themEH heterologously, as determined by immunoblotting. The cellclone BHK21-mEH/Mz1 had the highest level of mEH protein. Immuno-fluorescenceshowed that the level of expression was almost homogeneous throughoutthe cell population. Total protein isolated from the cell lineBHK21-mEH/Mzl had a specific mEH activity of 123 pmol/min/mgprotein, as determined with benzo[