High‐resolution imaging of the actin cytoskeleton and epithelial sodium channel, CFTR, and aquaporin‐9 localization in the vas deferens

Abstract

Vas deferens is a conduit for sperm and fluid from the epididymis to the urethra. The duct is surrounded by a thick smooth muscle layer. To map the actin cytoskeleton of the duct and its epithelium, we reacted sections of the proximal and distal regions with fluorescent phalloidin. Confocal microscopic imaging showed that the cylinder‐shaped epithelium of the proximal region has a thick apical border of actin filaments that form microvilli. The epithelium of the distal region is covered with tall stereocilia (13–18 µm) that extend from the apical border into the lumen. In both regions, the lateral and basal cell borders showed a thin lining of actin cytoskeleton. The vas deferens epithelium contains various channels to regulate the fluid composition in the lumen. We mapped the localization of the epithelial sodium channel (ENaC), aquaporin‐9 (AQP9), and cystic fibrosis transmembrane conductance regulator (CFTR) in the rat and mouse vas deferens. ENaC and AQP9 immunofluorescence were localized on the luminal surface and stereocilia and also in the basal and smooth muscle layers. CFTR immunofluorescence appeared only on the luminal surface and in smooth muscle layers. The localization of all three channels on the apical surface of the columnar epithelial cells provides clear evidence that these channels are involved concurrently in the regulation of fluid and electrolyte balance in the lumen of the vas deferens. ENaC allows the flow of Na+ ions from the lumen into the cytoplasm, and the osmotic gradient generated provides the driving force for the passive flow of water through AQP channels.

Measurement of Multi Ion Transport through Human Bronchial Epithelial Cell Line Provides an Insight into the Mechanism of Defective Water Transport in Cystic Fibrosis

“…According to Table 2, during 600 s of the experiment, 25% of 30 µL of chamber volume is transported across the 1.1 cm 2 cell layer in the form of 145 mM NaCl solution; this is equivalent to the movement of 10 15 ions per 1.1 cm 2 per second or 1.5 pA/µm 2 which can be delivered by a few open CFTR channels per µm 2 or a single VSOR or ORCC channels per few µm 2 . However, further studies of the mechanism of fluid transport are necessary e.g., on whether the water is transported transcellularly via aquaporins [20] or paracellularly. While our experiments considered drastic nonequilibrium conditions, similar mechanisms are likely to be involved in near-equilibrium conditions in the lungs.…”

Development and Differentiation of Epididymal Epithelial Cells in Korean Native Black Goat

“…Principal cells are the most abundant cell type in the epididymis. They secrete various proteins for sperm maturation and protection, and reabsorb and secrete bicarbonate and water via the cystic fibrosis transmembrane conductance regulator (CFTR) [3,4] and Aquaporin 9 (AQP9) [5,6], respectively, in the apical membrane of the epithelium. Clear cells are located throughout the epididymis and secrete protons into the lumen via V-ATPase located in their apical membrane [7].…”

Epithelial sodium channel (ENaC) in GtoPdb v.2021.2

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The epithelial sodium channels (ENaC) are located on the apical membrane of epithelial cells in the kidney tubules, lung, respiratory tract, male and female reproductive tracts, sweat and salivary glands, placenta, colon, and some other organs [9, 13,22,21,42]. In these epithelia, Na + ions flow from the extracellular fluid into the cytoplasm of epithelial cells via ENaC.

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“…In contrast to ENaC, CFTR (ion transporter defective in cystic fibrosis) is located on non-cilial cell-surface [15]. In the vas deferens segment of the male reproductive tract, the luminal surface is covered by microvilli and stereocilia projections with backbones composed of actin filament bundles [42]. In these cells, both ENaC and the water channel aquaporin AQP9 are localized on these projections and also in the basal and smooth muscle layers [42].…”

“…In the vas deferens segment of the male reproductive tract, the luminal surface is covered by microvilli and stereocilia projections with backbones composed of actin filament bundles [42]. In these cells, both ENaC and the water channel aquaporin AQP9 are localized on these projections and also in the basal and smooth muscle layers [42]. Thus, ENaC function is also essential for the clearance of respiratory airways, transport of germ cells, fertilization, implantation, and cell migration [15,22].…”