Effect of CYP2C9 Genetic Polymorphism in a Chinese Population on the Metabolism of Mestranol in vitro.
BACKGROUND
Mestranol is a widely used estrogen, which is converted into its active metabolite ethinyl estradiol by cytochrome P450 (CYP) 2C9. To comprehensively examine the enzymatic activity of reported CYP2C9 variants in Chinese individuals in response to mestranol, wild-type CYP2C9*1 and 35 allelic variants were highly expressed in Sf21 insect cell microsomes and used for the detection of their enzymatic values in vitro. These results showed that the majority of tested variants exhibited decreased clearance values compared to wild type, except for CYP2C9*40 and *36.


METHODS
Insect microsomes expressing the 36 CYP2C9 variants were incubated with 0.25-8 μmol/l mestranol for 30 min at 37°C. Then, the production of the metabolite of mestranol, ethinyl estradiol, was analyzed using high-performance liquid chromatography.


RESULTS
Most CYP-catalyzed reactions were sufficiently described by classical Michaelis-Menten kinetic parameters (e.g., Km and Vmax), while 9 variants exhibited atypical or non-Michaelis-Menten kinetic values, which were largely due to the self-inhibitory effect in response to mestranol.


CONCLUSIONS
This is the first report of these rare alleles for mestranol metabolism, which provides fundamental data for further clinical studies on CYP2C9 alleles for mestranol metabolism.
National Center for Clinical Laboratories, Beijing Hospital, Beijing, PR China.
Ji-Hong
JH
Hu
Li
L
Wang
Wan-Shu
WS
Li
Da-Peng
DP
Dai
Jian-Ping
JP
Cai
Guo-Xin
GX
Hu
D000818:Animals; D044466:Asian People / Q000235:genetics*; D065729:Cytochrome P-450 CYP2C9 / Q000235:genetics*; D004967:Estrogens / Q000378:metabolism*; D006801:Humans; D007313:Insecta; D008656:Mestranol / Q000378:metabolism*; D008861:Microsomes / Q000378:metabolism; D011110:Polymorphism, Genetic
D004967:Estrogens; D008656:Mestranol; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9