Microsomal epoxide hydrolase (mEH) is one of the major detoxification enzymes for epoxides. Polymorphism of EPHX has been associated with increases in the risk of several cancer incidences. Activity of this enzyme was reported potentially related to hormones. Currently, little information is available concerning to the association of polymorphism of EPHX or hormone levels with mEH activity in human. The purpose of this study was to fully characterize mEH activity in one month period among females. Six health adult females were recruited, and 8 ml of blood was repeatedly collected from each study subject on a regular period of 3– 4 days in one month. Blood samples were immediately separated into serum and red blood cells. mEH activity was determined by its catalysis of styrene oxide to styrene glycol in human erythrocyte cytosol. The concentration of styrene glycol was extracted using ethyl acetate and analyzed by an HPLC system connected to an UV detector. Genetic polymorphism of EHHX was also analyzed. Results show that mEH activity varied with time in each individual. Summarization of the variation patterns among the 6 subjects exhibits that mEH activity could be dependent on menstrual cycles despite of inter-individual variation, and further confirms that mEH activity is hormone-dependent in humans. The ongoing analysis of 11 hormones in serum collected from these 6 subjects using liquid chromatography coupled with tandem mass spectrometry will shed light on the relationships of mEH activity with hormone levels in females.
Date:
2004-06
Relation:
Toxicology and Applied Pharmacology. 2004 Jun;197(3):195.
