Androgen receptors and skeletal muscle composition in trotters treated with nandrolone laureate.

The research paper examines the impact of nandrolone laureate (a type of anabolic steroid) on muscle growth and androgen receptors in horses. It also investigates how this influence may vary throughout different times of the year.

Methodology

• Biopsy specimens were taken from the middle gluteal muscle of 6 Finnhorse trotters undergoing training before, immediately after, and 13 weeks after a 14-week treatment with nandrolone.
• Another six similarly trained horses served as controls, receiving no treatment.
• An additional twenty horses were used to evaluate annual variation in muscle concentration of androgen receptors (AR).
• The presence of AR was confirmed through immunohistochemical detection in the nuclei of the muscle cells.

Findings

• AR concentration remained constant during the initial 14 weeks of the study, but significantly increased in the 13-week follow-up period in both treatment and control groups. The researchers attribute this change to annual variation in AR.
• In horses treated with anabolic steroids, there was a significant increase in the cross-sectional area of type I muscle fibres during the treatment period. Moreover, the concentration of AR at the end of treatment correlated positively with the percentage of type IIA fibres, but this was not observed in the control group.
• The concentration of DNA was observed to decrease during the follow-up period. An increase in the percentage of H-chains in LDH isoenzymes and protein concentration was noted in horses treated with the steroids. These changes were not marked in control horses.
• No significant change in glycogen content and citrate synthase activity was observed as a result of the treatment.

Conclusions

• The use of anabolic steroids such as nandrolone laureate impacts type I and type II fibres differently in equine muscles.
• The concentration of AR in equine muscle may contribute to the observed changes in the middle gluteal muscles of horses undergoing treatment with steroids.

This research therefore helps unravel how the use of anabolic steroids leads to differing impacts on muscle fibre types, thereby informing the understanding of muscle growth and composition in equine athletes.