Metabolic studies of mesterolone in horses.
Abstract: Mesterolone (1alpha-methyl-5alpha-androstan-17beta-ol-3-one) is a synthetic anabolic androgenic steroid (AAS) with reported abuses in human sports. As for other AAS, mesterolone is also a potential doping agent in equine sports. Metabolic studies on mesterolone have been reported for humans, whereas little is known about its metabolic fate in horses. This paper describes the studies of both the in vitro and in vivo metabolism of mesterolone in racehorses with an objective to identify the most appropriate target metabolites for detecting mesterolone administration. In vitro biotransformation studies of mesterolone were performed by incubating the steroid with horse liver microsomes. Metabolites in the incubation mixture were isolated by liquid-liquid extraction and analysed by gas chromatography-mass spectrometry (GC-MS) after acylation or silylation. Five metabolites (M1-M5) were detected. They were 1alpha-methyl-5alpha-androstan-3alpha-ol-17-one (M1), 1alpha-methyl-5alpha-androstan-3beta-ol-17-one (M2), 1alpha-methyl-5alpha-androstane-3alpha,17beta-diol (M3), 1alpha-methyl-5alpha-androstane-3beta,17beta-diol (M4), and 1alpha-methyl-5alpha-androstane-3,17-dione (M5). Of these in vitro metabolites, M1, M3, M4 and M5 were confirmed using authentic reference standards. M2 was tentatively identified by mass spectral comparison to M1. For the in vivo metabolic studies, Proviron (20 tablets x 25 mg of mesterolone) was administered orally to two thoroughbred geldings. Pre- and post-administration urine samples were collected for analysis. Free and conjugated metabolites were isolated using solid-phase extraction and analysed by GC-MS as described for the in vitro studies. The results revealed that mesterolone was extensively metabolised and the parent drug was not detected in urine. Three metabolites detected in the in vitro studies, namely M1, M2 and M4, were also detected in post-administration urine samples. In addition, two stereoisomers each of 1alpha-methyl-5alpha-androstane-3,17alpha-diol (M6 and M7) and 1alpha-methyl-5alpha-androstane-3,16-diol-17-one (M8 and M9), and an 18-hydroxylated metabolite 1alpha-methyl-5alpha-androstane-3,18-diol-17-one (M10) were also detected. The metabolic pathway for mesterolone is postulated. These studies have shown that metabolites M8, M9 and M10 could be used as potential screening targets for controlling the misuse of mesterolone in horses.
Publication Date: 2007-06-03 PubMed ID: 17616252DOI: 10.1016/j.aca.2007.05.052Google Scholar: Lookup
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- Journal Article
Summary
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This research explores the metabolism of mesterolone, a synthetic anabolic androgenic steroid, in horses. Researchers carried out both in-vitro and in-vivo studies to understand how the steroid is processed within the horses’ bodies, with the ultimate aim of improving the detection of mesterolone doping in equine sports.
Study Method
- The researchers began with in vitro studies, where mesterolone was mixed with horse liver microsomes. They used liquid-liquid extraction to isolate the metabolites from the mixture, and gas chromatography-mass spectrometry (GC-MS) to perform a comprehensive analysis.
- The in vivo studies involved the oral administration of Proviron (a commercial name for mesterolone) to two thoroughbred geldings. Urine samples were collected before and after the administration. Similar to the in vitro studies, the samples were analysed using GC-MS technique.
Findings
- Five metabolites (M1-M5) were discovered in the in vitro studies, of which four (M1, M3, M4 and M5) were confirmed with reference standards. The fifth (M2) was identified tentatively through a comparison of its mass spectral data with M1.
- In the in vivo studies, three metabolites identified in the former studies (M1, M2 and M4) were also found in the post-administration urine samples, confirming their biological relevance and presence in the in vivo metabolism of mesterolone.
- Additionally, during the in vivo studies, the researchers uncovered five more metabolites (M6 to M10). M6 and M7 are stereoisomers of 1alpha-methyl-5alpha-androstane-3,17alpha-diol; M8 and M9 of 1alpha-methyl-5alpha-androstane-3,16-diol-17-one; and M10 is 1alpha-methyl-5alpha-androstane-3,18-diol-17-one, an 18-hydroxylated metabolite.
- It was noticed that mesterolone was fully metabolised, with no trace of the parent drug found in the horses’ urine samples.
Implications
- Understanding the metabolic pathway of mesterolone in horses can significantly improve detection methods for this steroid’s misuse in equine sports.
- The study suggests that using metabolites M8, M9 and M10 as screening targets could enhance the controlling methods for mesterolone abuse.
Cite This Article
APA
Ho EN, Leung DK, Leung GN, Wan TS, Wong HN, Xu X, Yeung JH.
(2007).
Metabolic studies of mesterolone in horses.
Anal Chim Acta, 596(1), 149-155.
https://doi.org/10.1016/j.aca.2007.05.052 Publication
Researcher Affiliations
- Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, NT, Hong Kong, China. emmie.nm.ho@hkjc.org.hk
MeSH Terms
- Anabolic Agents / metabolism
- Androsterone / analogs & derivatives
- Androsterone / urine
- Animals
- Doping in Sports
- Horses / metabolism
- Humans
- Male
- Mesterolone / metabolism
- Stereoisomerism
- Urinalysis
Citations
This article has been cited 1 times.- Yuan M, Breitkopf SB, Asara JM. Serial-omics characterization of equine urine.. PLoS One 2017;12(10):e0186258.
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