title: Analysis of exogenous nandrolone metabolite in horse urine by gas chromatography/combustion/carbon isotope ratio mass spectrometry.
abstract: Nandrolone (17beta-hydroxy-4-estren-3-one, NAD) is an endogenous steroid hormone; thus, the detection of its metabolites is not conclusive of NAD doping in racehorses. NAD doping control in male horses is based on the threshold, namely, the concentration ratio of 5alpha-estran-3beta,17alpha-diol (ETA) to 5(10)-estren-3beta,17alpha-diol (ETE). The ETA/ETE ratio of 1/1 was determined based on statistical data of authentic horses in International Federation of Horseracing Authorities. To individuals with complex metabolic disorders, however, such a threshold might not be applicable. The aim of this study was to establish an analytical method that discriminates endogenous steroids from exogenous ones in horse urine after NAD administration using gas chromatography/combustion/carbon isotope ratio mass spectrometry (GC/C/IRMS). Urine was sampled from NAD-administered and authentic horses. Ten millilitres of urine was hydrolyzed and subjected to liquid-liquid extraction and solid phase extraction. The residue of the extracts purified by HPLC was derivatized by acetylation. As a result of measurement of the (13)C/(12)C ratio (delta(13)C) by GC/C/IRMS, the delta(13)C values of ETA for NAD-administered and authentic horses were -32.20+/-0.35 per thousand and -27.85+/-0.75 per thousand (n=60), respectively. The detection limit of ETA in this GC/C/IRMS analysis was approximately 25 ng/ml. This study indicates that the measurement of delta(13)C by GC/C/IRMS enables us to discriminate exogenous ETA derived from NAD administration from endogenous ETA, proving that GC/C/IRMS is a useful technique to complement the ETA/ETE ratio.
authors: Laboratory of Racing Chemistry, 1731-2 Tsurutamachi, Utsunomiya, Tochigi 320-0851, Japan. m-yamada@lrc.or.jp
authors: Masayuki
authors: M
authors: Yamada
authors: Kenji
authors: K
authors: Kinoshita
authors: Masahiko
authors: M
authors: Kurosawa
authors: Koichi
authors: K
authors: Saito
authors: Hiroyuki
authors: H
authors: Nakazawa
mesh_terms: D045930:Anabolic Agents / Q000493:pharmacokinetics / Q000652:urine*; D000818:Animals; D001711:Biotransformation; D002247:Carbon Isotopes; D002851:Chromatography, High Pressure Liquid; D004300:Doping in Sports; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods* / Q000662:veterinary; D006736:Horses / Q000652:urine*; D008297:Male; D009277:Nandrolone / Q000493:pharmacokinetics / Q000652:urine*; D015813:Substance Abuse Detection / Q000379:methods* / Q000662:veterinary
chemical_list: D045930:Anabolic Agents; D002247:Carbon Isotopes; D009277:Nandrolone