Region‐Specific Expression of Aquaporin Subtypes in Equine Testis, Epididymis, and Ductus Deferens

Abstract

The process of water movement in the excurrent duct system of the male reproductive tract is pivotal for establishment of male fertility. The objective was to elucidate expression of aquaporin (AQP) water channels in the stallion reproductive tract. Real-time RT-PCR detected expression of AQP0-5 and AQP7-11 in testis, epididymis, and ductus deferens of mature stallions. There were two main expression patterns: (1) higher expression in testis than in epididymis and ductus deferens (AQP0, 24, 25, 28, 210, and 211); and (2) lower expression in testis than in epididymis and ductus deferens (AQP1, 23, 27, and 29). Overall, we inferred that fluid transport in the stallion testicle involved a collaboration of AQP subtypes (primarily AQP2, 25, 27, and 28). Based on immunohistochemistry, expression of AQP subtypes analyzed (i.e., AQP0, 22, 25, and 29) was localized to Leydig cells and elongated and round spermatids. Functional significance of AQP expression by Leydig cells remained uncertain. In elongated and round spermatids, AQP s likely contributed to the volume reduction observed during spermatogenesis. Subtypes AQP2 and AQP9 were the predominant forms expressed in epididymal tissue. Regulation of AQP2 expression, especially in the epididymal head, seemed to occur at the post-transcriptional level, as protein expression upon immunohistochemistry was pronounced, despite low transcript abundance. In epididymal tissue, AQPs likely contributed to fluid resorbtion, given their localization on the apical membrane of principal cells. Anat Rec, 296:1115Rec, 296: -1126Rec, 296: , 2013. V C 2013 Wiley Periodicals, Inc.Key words: stallion; aquaporin water channels; mRNA; protein Following completion of spermatogenesis, sperms leave the testis through the efferent ducts and enter the epididymis. During transit through the epididymis, spermatozoa undergo post-testicular maturation, including acquisition of progressive motility and the ability to undergo capacitation (Jones, 1998). These changes are due, at least in part, to changes in the composition of the epididymal luminal fluid microenvironment.

Aquaporin 9 is expressed in the epididymis of immature and mature pigs

“…The immunoreactivity of AQPs in the male reproductive tract has been intensively assessed in experimental animals and in primates, but little studied in domestic animals. Most prominent in this category of animals are studies of carnivores (Arrighi & Aralla, ; Arrighi, Aralla, Fracassetti, Mobasheri, & Cremonesi, ; Arrighi, Aralla , et al., ; Domeniconi, Orsi, Beu et al., ; Domeniconi et al., ), horses (Klein et al., ) and ruminants (Arrighi, Bosi, Accogli, et al., ; Schimming et al., ).…”

“…The immunodetection of AQPs in the genital tract of domestic animals has been identified both in males (Arrighi & Aralla, ; Arrighi, Aralla , Genovese, Picabea, & Bielli, ; Arrighi, Bosi, Accogli, et al., ; Domeniconi, Orsi, Beu, & Felisbino, ; Domeniconi, Orsi, Justulin, Beu, & Felisbino, ; Klein, Troedsson, & Rutllant, ; Schimming, Pinheiro, de Matteis, Machado, & Domeniconi, ) and females (Arrighi, Bosi, Frattini, Coizet, Groppetti, & Pecile, ); but there are no reports on immunolocalization of AQP expression in the porcine male reproductive tract. This study aimed to compare the morphology of epididymal epithelium, by light microscopy, and, for the first time, to identify the tissue distribution of AQP9 in the epididymal epithelium of piglets and boars.…”

Are the basal cells of the mammalian epididymis still an enigma?

“…The AQPs are a class of small, hydrophobic, integral membrane proteins that facilitate rapid passive movement of water. Studies have been performed mainly in rodents (Pastor-Soler et al 2001Badran and Hermo 2002;Hermo et al 2004Hermo et al , 2008Oliveira et al 2005;Da Silva et al 2006a, 2006bArrighi et al 2010a;Hermo and Smith 2011), primates (Fisher et al 1998), sporadically in carnivores (Domeniconi et al 2007(Domeniconi et al , 2008Arrighi et al 2010c;Arrighi and Aralla 2013) and very recently in the equine (Klein et al 2013) and bats (Oliveira et al 2013). Molecules, such as androgens, oestrogens and lumicrine factors, modulate the expression of genes involved in aquaporinmediated fluid absorption in the efferent ductules and the epididymis.…”

Immunolocalization of Aquaporins 1 and 9 in the Ram Efferent Ducts and Epididymis

“…The process of water movement in the excurrent duct of the male reproductive tract is important for the establishment of male fertility (Klein et al. ). Belleannée et al.…”

“…; Arrighi and Aralla ) and equine (Klein et al. ). Considering that the expression of AQPs in the reproductive tract of male ram has not been reported, the aim of this study was to investigate the immunolocalization of AQPs 1 and 9 in ram ED and epididymis.…”