A single GnRH-antagonist treatment affects testicular expression of Steroidogenic Acute Regulatory protein (StAR) and steroidogenic enzymes in dogs

M.W. ALBERTSEN; L.H. ANDERSEN; H. KÖRBER; M. FAYA; C. GOBELLO; S. GOERICKE-PESCH

Berlin

Congreso; 22nd Congress of the European Veterinary Society for Small Animal Reproduction 2019; 2019

European Veterinary Society for Small Animal Reproduction

Introduction and aim: Gonadotropin-releasing hormone (GnRH)-antagonists can suppress the production of gonadotropins from the pituitary gland. This results in a decreased production of testosterone and an impaired spermatogenesis in the testis. Therefore, GnRH-antagonists may have future potential for reproduction control in dogs (1). Steroidogenic acute regulatory protein (StAR) and steroidogenic enzymes are important factors for the synthesis of testosterone in the testis (2). However, the effect of GnRH-antagonist treatment on these factors has not been studied in dogs yet. This study investigates how a single treatment with the GnRH-antagonist acyline affects the expression of StAR and the steroidogenic enzymes cytochrome P450 side-chain cleavage (P450scc) and cytochrome P450 17α-hydroxylase/17,20-lyase (P450c17).Materials and methods: Testicular tissues from nine clinically healthy and sexually mature male dogs (4-6 years, 8-11 kg) were included. Four dogs were treated SC with a single injection of acyline (330 µg/kg) and castrated surgically 14 days after the treatment (AG; n=4). The remaining dogs served as a control group (CG; n = 5) and were castrated right after a clinical examination and semen collection/evaluation. Bouin?s solution fixed and paraffin embedded testicular tissue was used to study the expression of StAR, P450scc and P450c17 by immunohistochemistry. Light microscopy was used to evaluate spermatogenesis and to determine the localization of immunopositive cells. By use of the digital image processing program ImageJ, the percentage immunopositive area (PIA) and the intensity of the immunohistochemical staining (MGS-value) in the interstitial compartment were calculated. Additionally, the prevalence of immunopositive peritubular cells was calculated in each sample by evaluation of 200 peritubular cells. Results: Treatment resulted in a spermatogenic arrest. In regards to steroidogenesis, StAR, P450scc and P450c17 protein expression in Leydig cells was significantly affected 14 days after the treatment with acyline (P < 0.05). PIA was significantly lower for treated dogs compared to controls (StAR: P < 0.05; P450scc and P450c17: P