title: GC-MS-based quantitative signatures of cytochrome P450-mediated steroid oxidation induced by rifampicin.
abstract: BACKGROUND
  Drug-induced cytochrome P450 (CYP) activity affects endocrine function and drug clearance rates, leading to the development of unpredictable pathologic and toxicologic risks.
  
  
  METHODS
  Urinary steroid profiling based on gas chromatography-mass spectrometry (GC-MS) was used for simultaneous quantification of CYP-mediated regioselective hydroxysteroids and their substrates, including 26 androgens, 9 estrogens, 5 progestins, and 7 corticoids. The quantitative data were visualized using a hierarchically clustered heat map to allow identification of CYP-mediated steroid signatures. Twelve healthy subjects were orally administered 600 mg of rifampicin a day for 7 days, and their CYP enzyme activity was evaluated.
  
  
  RESULTS
  Using GC-MS, all 47 steroids were well separated with good peak shapes. This assay had good linearity (r > 0.994) in a dynamic range, and the interassay imprecision (% CV) and inaccuracy (% bias) were 3.0%-15.6% and 98.0%-109.2%, respectively. Administration of the CYP3A4 inducer rifampicin produced distinct differences in CYP3A4 and CYP11B1, CYP19A1, HSD11B, and HSD17B, which were indicated by their heat map-visualized steroid signatures.
  
  
  CONCLUSIONS
  This CYP-mediated steroid signature profile allows simultaneous assessment of CYP1A, CYP1B, CYP2C, CYP3A, CYP11B, CYP17A, CYP19A, and CYP21A in urine samples. This method could therefore be a useful tool for assessing drug efficacy.
authors.affiliation: Future Convergence Research Division, Korea Institute of Science and Technology, Yonsei University.
authors.forename: Ju-Yeon
authors.initials: JY
authors.lastname: Moon
authors.forename: Se Mi
authors.initials: SM
authors.lastname: Kang
authors.forename: Jeongae
authors.initials: J
authors.lastname: Lee
authors.forename: Joo-Youn
authors.initials: JY
authors.lastname: Cho
authors.forename: Myeong Hee
authors.initials: MH
authors.lastname: Moon
authors.forename: In-Jin
authors.initials: IJ
authors.lastname: Jang
authors.forename: Bong Chul
authors.initials: BC
authors.lastname: Chung
authors.forename: Man Ho
authors.initials: MH
authors.lastname: Choi
mesh_terms: D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006801:Humans; D006914:Hydroxysteroids / Q000378:metabolism*; D008297:Male; D010084:Oxidation-Reduction; D012293:Rifampin / Q000494:pharmacology*; D013256:Steroids / Q000378:metabolism*
chemical_list: D006914:Hydroxysteroids; D013256:Steroids; D003577:Cytochrome P-450 Enzyme System; D012293:Rifampin