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Somatostatin treatment affects testicular function in stallions
Jörg E Aurich1, Stefanie Kranski, Nahid Parvizi
1Clinic for Obstetrics, Gynecology and Andrology, University of Veterinary Sciences, Vienna, Austria.
Theriogenology
|March 7, 2003
Summary
Growth hormone (GH) regulation in stallions shows seasonal opioid influence, not seasonal basal levels. Decreased GH impacts semen motility and testosterone release, suggesting GH
Area of Science:
- Veterinary Endocrinology
- Reproductive Physiology
- Equine Science
Background:
- The regulation of growth hormone (GH) and its influence on testicular function in stallions are not fully understood.
- Investigating the somatotrophic axis is crucial for understanding stallion reproductive health.
Purpose of the Study:
- To investigate the regulation of GH release in stallions.
- To test the hypothesis that the somatotrophic axis influences testicular function.
- To explore seasonal and opioidergic modulation of GH release.
Main Methods:
- Studied basal plasma GH concentrations over 12 months in Shetland stallions (n=6).
- Administered octreotide (somatostatin analogue) to decrease GH release and assessed testicular function.
- Performed hCG stimulation tests to evaluate testosterone release post-octreotide treatment.
- Investigated opioidergic regulation of GH release using naloxone.
Main Results:
- No seasonal variations in basal plasma GH concentrations were observed.
- Octreotide treatment significantly decreased semen motility and reduced hCG-induced testosterone release.
- Naloxone injection increased GH release, with a stronger effect in June, indicating seasonal opioidergic modulation.
- No significant changes were found in ejaculate volume, density, sperm count, or morphology.
Conclusions:
- Stallion GH release is non-seasonal but modulated by season-dependent opioidergic mechanisms.
- Growth hormone plays a role in regulating testicular function in stallions, affecting semen quality and testosterone production.