TABLE 2

Apparent enzyme kinetics parameters of S-mephenytoin metabolism in pooled hepatic microsomes from 3- and 9-week-old wild-type and CYP2C18/CYP2C19 transgenic mice



3-Week-Old Animals

9-Week-Old Animals
Animal Pool
Vmax
Km
CLint
Vmax
Km
CLint
pmol/mg, min μM μl/mg, min pmol/mg, min μM μl/mg, min
wt male 12.4 8.5 1.46 9.9 29.1 0.34
tg male 13.2 14.0 0.94 15.7 20.3 0.77
wt female 22.4 11.9 1.88 9.9 30.0 0.33
tg female
16.6
8.7
1.90
7.5
30.7
0.24
  • wt, wild-type C57BL/6OlaHsd mice; tg, hemizygous CYP2C18/CYP2C19 transgenic mice. Each pool contains 5 to 10 mice (wild-type males and CYP2C18/CYP2C19 transgenic females 3 weeks old, n = 5; wild-type females 3 weeks old, n = 6; CYP2C18/CYP2C19 transgenic males 3 weeks old, n = 10; wild-type males and females 9 weeks old, n = 6; and CYP2C18/CYP2C19 transgenic males and females 9 weeks old, n = 8).