Steroidogenic Enzyme and Steroid Receptor Expression in the Equine Accessory Sex Glands.

Robyn E Ellerbrock,Barry A Ball,Igor F Canisso,Giorgia Podico,Mariano Carossino,Kirsten E Scoggin

doi:10.3390/ani11082322

Abstract

Simple SummaryThe accessory sex glands are responsible for producing seminal plasma, and thus play a vital role in reproduction and fertility. While the horse rarely suffers from some of the accessory sex gland diseases affecting other domesticated animals, glandular secretions can nonetheless affect semen quality and survival, and little is known about the effects of steroid hormones on glandular development and regulation. This study assessed the expression level and distribution of the steroid receptors AR, ESR1, and ESR2, and the steroidogenic enzymes 3ΒHSD, CYP17, and CYP19 in the equine accessory sex glands at various stages of life and demonstrated that sex steroid receptors are present in all equine glands throughout life. In contrast, steroidogenic enzymes were only weakly and variably expressed, suggesting that the accessory sex glands are not significant sites of steroidogenesis.The expression pattern and distribution of sex steroid receptors and steroidogenic enzymes during development of the equine accessory sex glands has not previously been described. We hypothesized that equine steroidogenic enzyme and sex steroid receptor expression is dependent on reproductive status. Accessory sex glands were harvested from mature stallions, pre-pubertal colts, geldings, and fetuses. Expression of mRNA for estrogen receptor 1 (ESR1), estrogen receptor 2 (ESR2), androgen receptor (AR), 3β-Hydroxysteroid dehydrogenase/Δ5-4 isomerase (3βHSD), P450,17α hydroxylase, 17–20 lyase (CYP17), and aromatase (CYP19) were quantified by RT-PCR, and protein localization of AR, ER-α, ER-β, and 3βHSD were investigated by immunohistochemistry. Expression of AR, ESR2, CYP17, or CYP19 in the ampulla was not different across reproductive statuses (p > 0.1), while expression of ESR1 was higher in the ampulla of geldings and fetuses than those of stallions or colts (p < 0.05). AR, ESR1 and ESR2 expression were decreased in stallion vesicular glands compared to the fetus or gelding, while AR, ESR1, and CYP17 expression were decreased in the bulbourethral glands compared to other glands. ESR1 expression was increased in the prostate compared to the bulbourethral glands, and no differences were seen with CYP19 or 3β-HSD. In conclusion, sex steroid receptors are expressed in all equine male accessory sex glands in all stages of life, while the steroidogenic enzymes were weakly and variably expressed.

Highlights

Accessory sex glands are located in the pelvic inlet and are primarily responsible for producing seminal plasma [1]
The colt prostate and ampulla had a higher epithelium to stromal ratio, and many sperm were noted in the lumen of the stallion ampulla
Some tubular dilation was noted in the gelding bulbourethral gland

Summary

Introduction

Accessory sex glands are located in the pelvic inlet and are primarily responsible for producing seminal plasma [1]. The ampulla is a prominent dilation of the vas deferens averaging 10–25 cm in length, 1–2 cm in width, and with a 2 mm luminal diameter [1,2]. Vesicular glands are sac-like structures located caudal to the ampulla on either side of the pelvic urethra and are responsible for producing the gel fraction of equine semen [1]. The prostate is a bi-lobulated gland located alongside the pelvic urethra, caudal to the vesicular glands, and originates as an outgrowth of the embryonic urogenital sinus [1]. The final accessory sex glands, the bulbourethral glands, are located at the caudal end of the pelvic urethra, and are covered by the bulbourethral muscle [1]

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