Postnatal Expression of Aquaporins in Epithelial Cells of the Rat Epididymis1

Abstract

The mammalian aquaporins (AQPs) are a family of 13 transmembrane channel proteins that are involved in the transport of water in numerous organs. In the male excurrent duct, the movement of fluid and solutes across the epithelium is essential for establishing the proper luminal environment in which sperm mature and are stored. AQP9 is abundantly expressed in the efferent ducts, the epididymis, and the vas deferens, where it could represent an important apical pathway for transmembrane water and solute movement. However, other organs in which water transport is critical, including the kidney, the lung, or the eye, express several different AQPs with a cell-specific pattern. To undertake a systematic analysis of the expression of known AQPs in the postnatal and adult rat epididymis, we examined the expression of their respective mRNAs in epithelial cells isolated by laser capture microdissection (LCM), and we determined their corresponding protein expression pattern by immunofluorescence and Western blotting. Our data show that, whereas AQP9 is the main AQP of the epididymis, the mRNA specific for Aqp2, 5, 7, and 11 are also expressed in epididymal epithelial cells. AQP5 protein colocalizes with AQP9 in the apical membrane of a subpopulation of principal cells in the corpus and cauda regions. Aqp2 mRNA was detected in epithelial cells after the second postnatal week and the amount significantly increased up to adulthood. However, AQP2 protein was detected only in the distal cauda of young rats (between the second and fourth postnatal week). No AQP2 protein was detected in the adult epididymis, indicating that posttranscriptional mechanisms are involved in the regulation of AQP2 expression. In addition, epididymal epithelial cells express significant amounts of the mRNAs coding for AQP7 and 11. No mRNA or protein for AQPs 0, 4, 6, and 8 were detectable in epithelial cells, and Aqp1 was detected in whole epididymal samples, but not in epithelial cells. Thanks to the recent development of microdissection technologies, our observations suggest that epididymal epithelial cells express several members of the AQP family with a region-specific pattern. AQPs may be involved not only in the transepithelial transport of water in the epididymis but also in the postnatal development of this organ, as suggested by the differential expression of AQP2.

Membrane Domain Specificity in the Spatial Distribution of Aquaporins 5, 7, 9, and 11 in Efferent Ducts and Epididymis of Rats

“…Results from this study agree with conclusions reached by a number of investigators that epithelial cells of the epididymis simultaneously express many AQPs to facilitate movement of water as part of the sperm transport and maturation process Da Silva et al 2006b). This includes AQP 5 and 9 by principal cells and AQP 3 by basal cells (Brown et al 1993;Fisher et al 1998;Elkjaer et al 2000Elkjaer et al ,2001Pastor-Soler et al 2001;Zhou et al 2001;Badran and Hermo 2002;Hermo et al 2004;Da Silva et al 2006a).…”

Calcitonin Has a Vasopressin-like Effect on Aquaporin-2 Trafficking and Urinary Concentration

“…82 In brief, the tissues were homogenized in Ambion TRI reagent, and RNA was isolated following the RiboPure kit protocol (Applied Biosystems, Foster City, CA). Genomic DNA contamination was eliminated using the Ambion DNA-free kit.…”

Is caveolin involved in normal proximal tubule function? Presence in model PT systems but absence in situ

“…To obtain enough material for PCR, two rounds of RNA amplification were carried out with a RiboAmp RNA amplification kit (Arcturus, catalog no. RA7011) as previously described (15). RNA from cell lines and isolated PT was extracted and purified with a RNeasy Mini Kit (Qiagen, catalog no.…”