Seasonal and Ageing‐Depending Changes of Aquaporins 1 and 9 Expression in the Genital Tract of Buffalo Bulls (Bubalus bubalis)

Abstract

The presence of Aquaporins 1 (AQP1) and 9 (AQP9), integral membrane water channels that facilitate rapid passive movement of water and solutes, was immunohistochemically detected in the excurrent ducts collected from sexually mature buffalo bulls of proven fertility during the mating (late autumn-winter) and non-mating (late spring to the beginning of autumn) seasons. Furthermore, the research was performed also on the epididymal cauda of a senile buffalo bull with inactive testis. Aquaporins 1 and 9 were immunolocalized at distinct levels. In the efferent ducts, AQP1 immunoreactivity was strongly evidenced at the apical surface of the non-ciliated cells and weakly along the basal membrane of the epithelial cells. The latter reactivity disappeared during the non-mating season. No AQP1 immunoreactivity was detected in the epithelium of epididymis and vas deferens, whereas AQP1 was expressed in the smooth muscle layer of the vas deferens. Aquaporin 1 was present in the blood vessels and in small nerve bundles all along the genital tract. The supranuclear zone of the epididymal principal cells was AQP9 immunoreactive, limited to the corpus and cauda regions, and vas deferens. The samples collected in the two reproductive seasons showed a weaker AQP9 immunoreactivity during the non-mating season. A typical AQP9 immunoreactivity was noticed in the old buffalo examined. The tested AQP molecules showed a different expression pattern in comparison with laboratory mammals, primates, equine, dog and cat. In addition, seasonal differences were noticed which are possibly useful in regard to the comprehension of the morphophysiology of reproduction in the bubaline species, which are still a matter of debate.

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

“…In the boar epididymis, the AQP9 is expressed in the nuclei of epithelial cells in the regions of the caput and cauda epididymis, whereas in the more distal region of the duct, the cauda epididymis, this protein was also immunolocated in the apical border of the epithelium lining, which was similar to that observed in the ram (Schimming et al., ). Arrighi, Bosi, Accogli, et al., () reported that in the buffalo epididymis, AQP9 does not show immunoreactivity in the caput epididymis region and presents weak reactivity in the corpus epididymis. These authors describe a strong immunoreactivity for AQP9 at the level of the apical surface of the cauda epididymis epithelium in the buffalo during the mating season.…”

“…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.…”

“…Among the AQPs expressed in the testis excurrent ducts, AQP9 is recognized as the primary AQP immunodetected in the epididymis (Arrighi, Bosi, Accogli, & Desantis, 2016;Pastor-Soler et al, 2010). In the adult rat epididymis, AQP9 was expressed in the rat efferent ducts and epididymis along the microvilli of the epididymal principal cells in all regions.…”

Aquaporins in the male reproductive tract and sperm: Functional implications and cryobiology

“…In the cat, AQP1 is present in the apical surface and lateral plasma membrane of the non‐ciliated cells of the efferent ducts, in the smooth muscle layer of the vas deferens and in the blood vessels of the entire male reproductive tract, and it is absent from the rete testis, the ciliated cells of the efferent ducts, the epididymis and vas deferens (Arrighi & Aralla, ; Arrighi, Ventriglia et al., ). In the buffalo, AQP1 is mainly localized in the apical surface (and to a lesser extent in the basal membrane) of the non‐ciliated cells of the efferent ducts, in the smooth muscle layer of the vas deferens, in the blood vessels of the entire male reproductive tract and in small nerve bundles, but it is absent from the epithelium of epididymis and vas deferens (Arrighi, Bosi, Accogli, & Desantis, ). The absence of AQP1 in germ cells of most mammals contrasts with bats, where AQP1 has been found in spermatids (Oliveira, Campolina‐Silva, Nogueira, Mahecha, & Oliveira, ).…”