Table 4

Comparison of the abilities of cDNA-expressed P450 to activate aflatoxin B1 to a gene mutagen

EnzymeCell Line(A) Minimum Effective Concentration(B) P450 ContentProduct of A × BReference No.
ng/ml pmol/mg microsomes
CYP1A1h1A16212740 49
CYP1A2h1A2/Hyg10.51.415 53
CYP2A62A3/Hol7554-a 385 46
CYP2B6h2B638552090This  study
CYP3A43A4/Hol881.7150 53

The minimum effective concentration was calculated as the aflatoxin concentration where the dose response curve crossed the 99% upper confidence limit for the historical negative control data base (7 × 10−6). All cell lines seem to have similar negative control mutant frequencies.

  • 4-a C. Crespi, unpublished data.