Steroidogenic Enzyme and Steroid Receptor Expression in the Equine Accessory Sex Glands.
Authors: Ellerbrock Robyn E, Podico Giorgia, Scoggin Kirsten E, Ball Barry A, Carossino Mariano, Canisso Igor F
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Understanding how stallions produce and respond to sex hormones requires knowledge of the specialised tissues involved, yet the expression of key steroidogenic enzymes and steroid receptors in equine accessory sex glands—the ampulla, vesicular glands, bulbourethral glands, and prostate—had never been systematically characterised across different reproductive statuses. Ellerbrock and colleagues harvested tissue from mature stallions, pre-pubertal colts, castrated geldings, and equine fetuses, then used molecular techniques (reverse transcription PCR and immunohistochemistry) to map where six critical molecules—two oestrogen receptors, the androgen receptor, and three steroidogenic enzymes—were expressed and localised within these glands. Contrary to the researchers' hypothesis, most steroidogenic enzyme expression remained consistent regardless of reproductive status, though notably oestrogen receptor alpha (ESR1) was significantly elevated in the ampulla of geldings and fetuses compared with intact animals (p < 0.05), and androgen receptor expression was notably lower in the vesicular and bulbourethral glands of stallions relative to other reproductive states. All steroid receptors were present across all glands and developmental stages, suggesting these tissues retain hormone-responsiveness throughout life, whilst the weak and inconsistent steroidogenic enzyme expression indicates that local hormone production within these glands may be minimal and not a key regulatory mechanism. For practitioners, these findings suggest that the accessory sex glands' function is primarily dependent on responding to circulating hormones rather than synthesising them locally, which has implications for understanding erectile function, semen quality, and the physiological changes observed following castration.
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Practical Takeaways
- •Understanding steroid receptor expression patterns in stallions versus geldings may inform clinical assessment of accessory gland pathology and reproductive hormone responsiveness
- •The weak steroidogenic enzyme expression in accessory glands suggests these tissues are primarily responsive to circulating hormones rather than locally producing steroids
- •Differential receptor expression across gland types indicates tissue-specific hormone sensitivity that may be clinically relevant for conditions affecting the prostate, seminal vesicles, or bulbourethral glands
Key Findings
- •Sex steroid receptors (AR, ESR1, ESR2) are expressed in all equine male accessory sex glands across all life stages from fetus to mature stallion
- •ESR1 expression was significantly higher in the ampulla of geldings and fetuses compared to stallions and colts (p < 0.05)
- •Steroidogenic enzymes (CYP17, CYP19, 3β-HSD) showed weak and variable expression across reproductive statuses and glandular tissue types
- •AR, ESR1, and CYP17 expression were decreased in bulbourethral glands compared to other accessory sex glands