Immunolocalisation and expression of oxytocin receptors and sex hormone-binding globulin in the testis and epididymis of dogs: correlation with sperm function

Abstract

The aim of this study was to confirm gene and protein expression of oxytocin receptor (OTR) and sex hormone-binding globulin (SHBG) in the testis and epididymis of dogs, correlating these data with sperm quality and production and testosterone concentrations. Positive correlations were found between OTR and SHBG expression in both the testis and epididymis. Testicular OTR expression was positively associated with plasma membrane and acrosome integrity in canine spermatozoa, whereas SHBG expression in the testis was positively correlated with various sperm characteristics, such as sperm concentration, total and progressive motility, plasma membrane integrity and acrosome integrity. Testicular expression of both OTR and SHBG was negatively correlated with low sperm mitochondrial activity. In the epididymis, SHBG expression was only positively correlated with plasma membrane integrity. Analysis of protein expression revealed that testicular OTR was positively correlated with testosterone concentrations and negatively correlated with the absence of sperm mitochondrial activity. In addition, SHBG expression in the testes was associated with epididymis SHBG expression and morphologically normal cells. Immunohistochemical (IHC) analysis revealed the presence of both OTR and SHBG in testicular smooth muscles and Leydig cells. However, in the epididymis, OTR was only located in smooth muscle cells, whereas neither IHC nor western blotting detected SHBG. Together, the results of this study suggest that OTR and SHBG play key roles in spermatogenesis and sperm maturation, being essential for male reproductive success.

Expression of oxytocin receptors and oxytocin assisted electroejaculation in the domestic cat (Felis catus)

“…The presence and localization of these receptors in the testis and efferent ducts reflect the essential roles of oxytocin in spermatogenesis (Anjum et al., 2018) and sperm transport (Frayne et al., 1996; Kunz et al., 2007; Thackare et al., 2006). Immunohistochemical localization of OTRs in reproductive tracts of male animals has been revealed in several studies such as in mice (Ang et al., 1991; Assinder et al., 2002), rats (Foo et al., 1991), rams (Assinder et al., 2000), dogs (Dalmazzo et al., 2019) and stallions (Jung & Yoon, 2021). However, differences in terms of localization and functions have consistently been reported among species.…”

Systematic review of hormonal strategies to improve fertility in rams

“…This hormone contracts the smooth muscle of the uterus and mammary gland, which is important for sperm transport after copulation as well as facilitating labour and udder contractions ( Stadler et al, 2020 ). Similarly, Ox is produced by Leydig cells, the epididymis and the prostate, where its receptors are found ( Knickerbocker et al, 1988 ), and increases the contractions of the seminiferous tubules and the walls of the epididymal ducts, thus facilitating the transfer of spermatozoa ( Stadler et al, 2020 ; Assinder et al, 2000 ; Dalmazzo et al, 2019 ; Ruan et al, 2020 ). It is frequently used today, especially in male reproduction in small ruminants, in different aspects, such as for semen collection with the electro-ejaculator, where, when used together with the prostaglandin (PG) before semen collection, it reduces the time and number of electrical stimuli required to obtain a semen sample without affecting its quality, both in goat bucks ( Ruan et al, 2020 ) and rams ( Abril-Sánchez et al, 2019 ; Luna-Palomera et al, 2021 ).…”

“…Oxytocin is produced locally in Leydig cells and is under the control of LH and lipoproteins but not T ( Stadler et al, 2020 ). It regulates basal epididymal contractility and stimulates sperm release from the storage site in the epididymis at the time of ejaculation ( Knickerbocker et al, 1988 ; Dalmazzo et al, 2019 ; Stadler et al, 2020 ). Application of Ox prior to semen collection can increase sperm concentration in several mammalian species including rams, rabbits, cattle and buffalo ( Luna-Palomera et al, 2021 ).…”

Revisiting the gonadotropic regulation of mammalian spermatogenesis: evolving lessons during the past decade

“…T is essential for suppression of AMH (156,157), pubertal maturation of testicular somatic cells (e.g.-PTc, Sc, Lc in developmental order) (2), the establishment of Blood-testis barrier (BTB) (158), meiotic progression of Gc and spermiation (159). The free titer of T depends upon the extent of the presence of sex hormone-binding globulin (SHBG) which binds to T with strong affinity; thus, SBHG regulates the process of spermatogenesis by controlling the serum concentration of biologically active T (160,161). The absolute requirement of T on male fertility has been confirmed from ARKO (ubiquitously lacking AR) mice (93, 94).…”