Studies related to the metabolism of anabolic steroids in the horse: testosterone.

The research article discusses a study on the metabolism of testosterone, an anabolic steroid, in horses. The study traces the excretion and neutral metabolites of testosterone after its intramuscular administration.

Administration and Excretion of Testosterone

After the administration of [4-14C]testosterone, a radiolabeled form of testosterone used for tracking purposes, to two gelded cross-bred horses, the researchers measured the excretion of the testosterone in the urine of the horses. The key findings were:

• A substantial amount, about 45%, of the administered testosterone was expelled from the body through urine within the first 96 hours.
• Traces of urinary activity resulting from the administration could still be observed at 200 hours, suggesting a long duration of testosterone metabolite presence in the bodies of horses.

Analysis of Neutral Metabolites

Two procedures were employed to analyze the urine samples for neutral metabolites of testosterone: enzyme hydrolysis and acid hydrolysis. Highlights of the results were:

• By applying gas-liquid chromatography and mass spectrometry (g.l.c.-mass spectrometry), the research team was able to study the metabolites that were formed after the breakdown of testosterone.
• The metabolite 5 alpha-Androstane-3 beta, 17 alpha-diol was only detectable in the sample that had undergone enzyme hydrolysis. On the other hand, testosterone was only found in the sample that had undergone acid hydrolysis.
• Two metabolites, namely 5 alpha-Androstane-3 beta, 17 beta-diol and 3 beta-hydroxy-5 alpha-androstan-17-one, were found primarily in the acid-hydrolysable extract.

The results of the study contribute to understanding how testosterone is metabolized and excreted in horses, which is important for maintaining the health of these animals and for making decisions related to veterinary care, breeding, and sport regulations.