title: Inhibitory potential of chlormadinone acetate (CMA) on five important UDP-glucuronosyltransferases in human liver.
abstract: Chlormadinone acetate (CMA), a derivative of 17-a-hydroxyprogesterone, has been widely used as an orally effective progestogen in hormone replacement therapy (HRT). Glucuronidation catalyzed by UDP-glucuronosyltransferases (UGTs) is one of the major steps responsible for the metabolism of many drugs, environmental chemicals and endogenous compounds. Pharmacokinetic behaviours of drugs could be altered by inhibition of these UGT isoforms, and the search for drugs that potentially inhibit these UGT isoforms is very significant from a clinical point of view. In the present study, inhibition of five important UGT isoforms in human liver (UGT1A1, 1A3, 1A6, 1A9 and 2B7) by CMA was investigated using 4-MU as nonspecific substrate and recombinant UGT isoforms as enzyme sources. The results showed that CMA exhibited inhibitory effects on UGT1A3 (IC50 = 8.6 +/- 1.4 microM) and UGT2B7 (IC50 = 14.2 +/- 3.8 microM), with other UGT isoforms negligibly influenced. Lineweaver-Burk and Dixon plots showed that CMA noncompetitively inhibited UGT1A3 and UGT2B7. The Ki value was calculated to be 36.9 microM and 4.1 microM for UGT1A3 and UGT2B7, respectively. Considering that UGT1A3 and UGT2B7 are involved in the metabolism of many drugs, special attentions should be paid when CMA was co-administered with the drugs which mainly underwent UGT1A3, 2B7-mediated metabolism.
authors.affiliation: National Population and Family Planning Key Laboratory of Contraceptives Drugs & Devices, Shanghai Institute of Planned Parenthood Research, Shanghai, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Huang
authors.forename: Zhong-Ze
authors.initials: ZZ
authors.lastname: Fang
authors.forename: Yan-Yan
authors.initials: YY
authors.lastname: Zhang
authors.forename: Liang-Liang
authors.initials: LL
authors.lastname: Zhu
authors.forename: Ling-Lin
authors.initials: LL
authors.lastname: Feng
authors.forename: Wei
authors.initials: W
authors.lastname: Zheng
authors.forename: Yun-Feng
authors.initials: YF
authors.lastname: Cao
authors.forename: Dong-Xue
authors.initials: DX
authors.lastname: Sun
authors.forename: Ling
authors.initials: L
authors.lastname: Yang
mesh_terms: D002715:Chlormadinone Acetate / Q000494:pharmacology*; D003278:Contraceptives, Oral, Hormonal / Q000494:pharmacology*; D014453:Glucuronosyltransferase / Q000037:antagonists & inhibitors*; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D003278:Contraceptives, Oral, Hormonal; D007527:Isoenzymes; D002715:Chlormadinone Acetate; D014453:Glucuronosyltransferase