Metabolic studies of turinabol in horses.

The research conducted analyses the metabolism of a synthetic, orally administered anabolic androgenic steroid, Turinabol, in horses. The objective of the study was to identify the most significant metabolites for detecting the usage of Turinabol in horse racing sport.

Methodology

• The research was conducted through both in vitro and in vivo studies. In the in vitro experiment, Turinabol was subjected to horse liver microsomes. After Turinabol’s incubation, the metabolites were isolated by a process known as liquid-liquid extraction and then analysed using gas chromatography-mass spectrometry (GC-MS).
• In the in vivo studies, the researchers administered turinabol orally to two horses. Urine samples were collected both before and after administration for analysis. Metabolites in the urine were isolated through solid-phase extraction and then examined using the same technique as in the in vitro studies (GC-MS).

Findings

• The in vitro studies showed that the major biotransformation of turinabol was hydroxylation at the C6, C16 and C20 sites which produced metabolites 6beta-hydroxyturinabol, 20-hydroxyturinabol, two stereoisomers of 6beta,16-dihydroxyturinabol and 6beta,20-dihydroxyturinabol. The metabolite 6beta-hydroxyturinabol was validated using an authentic reference standard while the structures of the other metabolites were identified using mass spectral interpretation.
• The in vivo studies demonstrated that turinabol was extensively metabolised and the parent drug could not be detected in urine. The two metabolites detected in the in vitro studies, 20-hydroxyturinabol and 6beta,20-dihydroxyturinabol were also detected in post-administration urine samples. Additionally, 17-epi-turinabol and six other metabolites derived from D-ring hydroxylation and A-ring reduction were detected. These metabolites have not been reported in any species except for 17-epi-turinabol.
• All in vivo metabolites were detected within 48 hours following administration.

Implications

• This research has practical implications for racehorse doping controls. By understanding the metabolism of turinabol in horses, officials can detect its use more effectively.
• The identified metabolites can serve as targets for testing. It further provides a broader understanding of how synthetic steroids behave in a horse’s body, contributing valuable knowledge to the field of equine sports science.