Effects of NADPH preincubation on the production
of resorufin by
P450 1A1 in the presence of ethynylflavones. Five-minute preincubation
was applied in the presence (red triangles) and absence (blue squares)
of NADPH for each test. The concentrations used for 2′EF, 3′EF,
4′EF, 5EF, 6EF, and 7EF were 0.1 μM, 0.00625 μM,
0.00625 μM, 0.1 μM, 0.00625 μM, and 0.00625 μM,
respectively. For 2′EF, preincubation with NADPH exhibited
a slight influence on enzymatic activity of P450 1A1. For 5EF, preincubation
with NADPH caused a considerable inhibition of P450 1A1. Whereas for
3′EF, 4′EF, 6EF, and 7EF, 5 min preincubation with NADPH
(0.00625 μM of inhibitor) lead to a complete inhibition of P450
1A1.