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Immunolocalization and expression of oxytocin receptors (OTR) and sex hormone- binding globulin (SHBG) in the testicle and epididymis of dogs: correlation with sperm quality

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Author(s):
Andressa Dalmazzo
Total Authors: 1
Document type: Doctoral Thesis
Press: São Paulo.
Institution: Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD)
Defense date:
Examining board members:
Valquiria Hyppólito Barnabe; Bruno Cogliati; Silvia Edelweiss Crusco; Claudia Kiyomi Minazaki; Ricardo José Garcia Pereira
Advisor: Valquiria Hyppólito Barnabe
Abstract

Oxytocin (OT) is a hypothalamic neuropeptide that plays important and well known roles in the female such as uterine contraction during childbirth and milk ejection. Notwithstanding, studies have shown important endocrine and paracrine functions also in the male reproductive tract, highlighted by the possible joint action between OT and sex hormone-binding globulin (SHBG). In dogs, however, there is no information available with regards to the role of these hormones in the reproductive function. Thus, studies directed to oxytocin (OTR) and SHBG receptors and their functions in the male reproductive system, specifically with regards to sperm physiology. Such knowledge is essential to understand the reproductive physiology for the subsequent use in reproductive biotechnologies in small animals and humans, especially by providing new perspectives for the therapeutic use of oxytocin in reproductive disorders. Therefore, the aim of this study is to assess the gene and protein expression of OTR and SHBG in the testis and epididymis of dogs, correlating these data with sperm quality and testosterone dosage. To this end, testis and epididymis were collected from 26 dogs in reproductive age (1 to 5 years). After orchiectomy, collection of sperm from the cauda epididymis was carried out and then the samples were analyzed for computerized motility of semen (CASA), plasma membrane integrity (eosin / nigrosine), acrosome membrane integrity (Fast Green / rose Bengal) and mitochondrial activity (3\'3 Diaminobenzidine). The immunolocalization of OTR and SHBG was performed by immunohistochemistry and immunofluorescence. Gene expression analysis was performed by real time polymerase chain reaction (qRT - PCR). The protein expression was further assessed by Western Blotting. Significant positive correlations were found between the gene expressions of OTR and SHBG in both the testis and epididymis. Furthermore, the OTR expression in testis was positively correlated to sperm with intact acrosome membrane and negatively to the percentage of cells with low mitochondrial activity. On the other hand, testicular SHBG was positively correlated with sperm concentration, percentage of sperm with intact plasma membrane and acrosome, motility, progressive motility and the percentage of RAPID sperm. Also, negative correlation was found between testicular SHBG and the percentage of cells with low mitochondrial activity. Furthermore, in the epididymis, SHBG gene expression was positively correlated to the percentage of cells with intact plasma membrane and protein expression of SHBG in the testis. In relation to the protein expression, the OTR in the testis correlated positively with blood plasma testosterone and negatively with sperm with no mitochondrial activity. In the epididymis, OTR protein expression correlated positively with sperm showing intact acrosome and negatively with cells with no mitochondrial activity. With regards to SHBG proteins expression, there was a positive correlation to SHBG gene expression in the epididymis, normal cells and some patterns of sperm velocity. In the immunohistochemistry, we observed the OTR and SHBG immunostainings in the smooth muscle and Leydig cells of the testis while, in the epididymis, the OTR immunostaining could be observed only in the smooth muscle. Interestingly, there was no immunostaining or protein expression of SHBG in the epididymis. Our results demonstrated that OTR and SHBG are expressed in the testis and epididymis of dogs and are related to important sperm functions, essential for reproductive success (AU)

FAPESP's process: 13/00888-1 - Correlation between oxytocin receptors expression (OTR) in the testicles and epididymis in dogs and semen quality
Grantee:Andressa Dalmazzo
Support type: Scholarships in Brazil - Doctorate