Table 1

Effects of P450 inhibitors and anti-P450 antibodies on oxidation of phenytoin and 4′-HPPH by rat liver microsomes

AdditionProduct Formation
4′-HPPH from Phenytoin3′,4′-diHPPH from 4′-HPPH
μM pmol/min/mg protein
(I) Chemical
 None1-a 144 (100)292 (100)
 SKF-525A5031 (21)92 (31)
 Metyrapone50112 (78)207 (71)
mg IgG/nmol P450 pmol/min/nmol P450
(II) Antibody
 None1-b 239 (100)287 (100)
 Preimmune20233 (98)361 (126)
 Anti-CYP2C20105 (44)102 (28)
 Anti-CYP3A20184 (81)200 (70)

Phenytoin (100 μM) or 4′-HPPH (100 μM) was incubated with rat liver microsomes in the presence of chemicals or antibodies. Results are presented as means of duplicate determinations. Values in parentheses indicate percentage of control activities (none).

  • 1-a  0.8 μM of total P450.

  • 1-b  0.08 μM of total P450.