Abstract
Previously (Wellner et al., Pflugers Arch 441:49–56, 2000) we suggested that the localization of the aquaporins (AQPs) AQP5 and AQP8 in the apical and basolateral membranes of rat submandibular gland (SMG) acinar cells, respectively, provides for transcellular water flow during saliva formation. While the localization of AQP5 in this gland has been verified in several laboratories, there have been differing reports regarding AQP8 localization. Other investigators subsequently reported that AQP8 is not expressed in the acinar or ductal cells of the major salivary glands of the rat, but in the myoepithelium of each gland. Thus, we have carried out additional studies: (1) to reassess the localization of AQP8 in the rat SMG and (2) to assess the localization of AQP8 in the rat parotid gland (PG). Initially, we compared the localizations of AQP8 with recognized basolateral markers in acinar cells [the Na+,K+-ATPase and the Na+–K+–2Cl− cotransporter (NKCC1)]. Our results indicated that Na+,K+-ATPase localized in both the basal and lateral membranes of rat SMG acinar cells, whereas AQP8 was detected only in the basal regions of the acini. In the rat PG, AQP8 was invested near intercalated ducts and adjacent acini, whereas NKCC1 localized in the basolateral membranes of acinar cells. As these results were suggestive of myoepithelial localization in both glands, we compared AQP8 localization with the localization of smooth muscle actin, a myoepithelial marker. We found that AQP8 and smooth muscle actin colocalized in both the rat SMG and PG, providing additional strong support for a myoepithelial localization of AQP8. Thus, in agreement with an earlier report by other investigators (Elkjaer et al., Am J Physiol Renal Physiol 281:F1047–F1057, 2001), we report that AQP8 is expressed in the myoepithelial cells, but not in the acinar cells, of both the rat SMG and PG.
References
Elkjaer M-L, Nejsum LN, Gresz V, Kwon T-H, Jensen UB, Froklaer J, Nielsen S (2001) Immunolocalization of aquaporin-8 in rat kidney, gastrointestinal tract, testis, and airways. Am J Physiol Renal Physiol 281:F1047–F1057
Gresz V, Kwon TH, Hurley PT, Varga G, Zelles T, Nielsen S, Case RM, Steward MC (2001) Identification and localization of aquaporin water channels in human salivary glands. Am J Physiol Gastrointest Liver Physiol 281:G247–G254
King LS, Kozono D, Agre P (2004) From structure to disease: the evolving tale of aquaporin biology. Nat Mol Cell Biol 5:687–698
Koyama Y, Yamamoto T, Kondo D, Funaki H, Yaoita E, Kawasaki K, Sato N, Hatakeyama K, Kihari I (1997) Molecular cloning of a new aquaporin from rat pancreas and liver. J Biol Chem 272:30329–30333
Redman RS (1994) Myoepithelium of salivary glands. Microsc Res Tech 27:25–45
Takata K, Matsuzaki T, Tajika Y (2004) Aquaporins: water channels of the cell membrane. Prog Histochem Cytochem 39:1–83
Wellner RB, Hoque AT, Goldsmith CM, Baum BJ (2000) Evidence that aquaporin-8 is located in the basolateral membrane of rat SMG acinar cells. Pflugers Arch 441:49–56
Yang B, Song Y, Zhao D, Verkman AS (2005) Phenotype analysis of aquaporin-8 null mice. Am J Physiol Cell Physiol 288:1161–1170
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Wellner, R.B., Redman, R.S., Swaim, W.D. et al. Further evidence for AQP8 expression in the myoepithelium of rat submandibular and parotid glands. Pflugers Arch - Eur J Physiol 451, 642–645 (2006). https://doi.org/10.1007/s00424-005-1489-0
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DOI: https://doi.org/10.1007/s00424-005-1489-0