Table 3

Effects of phenytoin administration on P450, NPR, and b5contents and typical drug oxidation activities in rat liver microsomes

UntreatedPhenytoin-Treated
nmol/mg protein
(I) Protein Contents
 Total P4503-a 0.75  ± 0.08 (100)1.43  ± 0.243-160 (191)
 CYP1A3-b 0.04  ± 0.01 (100)0.04  ± 0.02 (100)
 CYP2B3-b 0.07  ± 0.02 (100)1.01  ± 0.163-160 (1440)
 CYP2C3-b 0.25  ± 0.05 (100)0.22  ± 0.05 (89)
 CYP2E13-b 0.17  ± 0.02 (100)0.21  ± 0.05 (123)
 CYP3A3-b 0.23  ± 0.06 (100)0.46  ± 0.153-150 (199)
 NPR3-c 0.11  ± 0.02 (100)0.17  ± 0.013-160 (155)
b 5 3-a 0.06  ± 0.02 (100)0.04  ± 0.02 (67)
nmol/min/mg protein
(II) Drug Oxidation Activities
 7-EthoxycoumarinO-deethylation1.05  ± 0.09 (100)2.58  ± 0.323-160 (246)
 EthoxyresorufinO-deethylation0.26  ± 0.02 (100)0.36  ± 0.073-150 (138)
 Testosterone 16β-hydroxylation0.05  ± 0.01 (100)1.10  ± 0.243-160 (2200)
 Testosterone 16α-hydroxylation0.42  ± 0.03 (100)1.15  ± 0.203-160 (274)
 Anilinep-hydroxylation0.12  ± 0.01 (100)0.12  ± 0.01 (100)
 Testosterone 6β-hydroxylation1.10  ± 0.22 (100)3.82  ± 0.863-160 (347)
 Styrene oxide hydration23.4  ± 0.9 (100)51.4  ± 5.73-160 (220)

Data are mean ± S.D. for four male rats treated with oral administration of phenytoin (300 mg/kg/day) for 20 days. Values in parentheses indicate percentage of control (untreated).

  • Significantly different from untreated male rats (

  • 3-150p < 0.05;

  • 3-160p < 0.01).

  • 3-a  Determined spectrally.

  • 3-b  Determined immunochemically.

  • 3-c  Calculated by NADPH-cytochromec reduction activities.