Aquaporin 9 Expression along the Male Reproductive Tract1

Abstract

Fluid movement across epithelia lining portions of the male reproductive tract is important for modulating the luminal environment in which sperm mature and reside, and for increasing sperm concentration. Some regions of the male reproductive tract express aquaporin (AQP) 1 and/or AQP2, but these transmembrane water channels are not detectable in the epididymis. Therefore, we used a specific antibody to map the cellular distribution of another AQP, AQP9 (which is permeable to water and to some solutes), in the male reproductive tract. AQP9 is enriched on the apical (but not basolateral) membrane of nonciliated cells in the efferent duct and principal cells of the epididymis (rat and human) and vas deferens, where it could play a role in fluid reabsorption. Western blotting revealed a strong 30-kDa band in brush-border membrane vesicles isolated from the epididymis. AQP9 is also expressed in epithelial cells of the prostate and coagulating gland where fluid transport across the epithelium is important for secretory activity. However, it was undetectable in the seminal vesicle, suggesting that an alternative fluid transport pathway may be present in this tissue. Intracellular vesicles in epithelial cells along the reproductive tract were generally poorly stained for AQP9. Furthermore, the apical membrane distribution of AQP9 was unaffected by microtubule disruption. These data suggest that AQP9 is a constitutively inserted apical membrane protein and that its cell-surface expression is not acutely regulated by vesicular trafficking. AQP9 was detectable in the epididymis and vas deferens of 1-wk postnatal rats, but its expression was comparable with adult rats only after 3--4 wk. AQP9 could provide a route via which apical fluid and solute transport occurs in several regions of the male reproductive tract. The heterogeneous and segment-specific expression of AQP9 and other aquaporins along the male reproductive tract shown in this and in our previous studies suggests that fluid reabsorption and secretion in these tissues could be locally modulated by physiological regulation of AQP expression and/or function.

Identification of novel Prominin-1/CD133 splice variants with alternative C-termini and their expression in epididymis and testis

“…5D, boxes) and the epithelia of the corpus and caput (data not shown) were prominin-1 negative. This discontinuous expression pattern is reminiscent of that described for the water channel protein aquaporin 9, which is expressed only by principal and not by clear cells (Pastor-Soler et al, 2001).…”

Metabolic impact of the glycerol channels AQP7 and AQP9 in adipose tissue and liver

“…Several observations of AQP monomers forming a homotetrameric organization in the membrane have been made (Engel et al 2000), and this feature is probably similar for all members of the AQP family. Transport through AQPs is not an active process and is dependent on the presence of a gradient across the membrane in question (Pastor-Soler et al 2001).…”

Pattern Recognition Receptor–Initiated Innate Antiviral Responses in Mouse Epididymal Epithelial Cells

“…Fibroblasts in the primary cultures were limited by adding 0.1 mg/ml collagenase IV in the culture medium during the first 24 h of culture. The culture medium was changed every day for EEC proliferation for 4 d. The purities of major cell types in the EECs were determined using immunostaining of molecular markers, including aquaporin 9 (for principal cells) (25), keratin 5 (for basal cells) (26), and F4/80 (for macrophages) (27). Triplicate stains were performed for each cell isolation, and at least 200 total cells were spontaneously counted for each staining.…”