Regular Article
Immunolocalization of AQP9 in Liver, Epididymis, Testis, Spleen, and Brain

https://doi.org/10.1006/bbrc.2000.3505Get rights and content

Abstract

The aims of this study were to determine the cellular and subcellular localization of aquaporin-9 (AQP9) in different rat organs by immunoblotting, immunohistochemistry and immunoelectron microscopy. To analyze this, we used rabbit antibodies to rat AQP9 raised against three different AQP9 peptides (amino acids 267–287, 274–295, and 278–295). In Cos7 cells transfected with rat AQP9, the affinity-purified antibodies exhibited marked labeling, whereas nontransfected cells and cells transfected with aquaporin-8 (AQP8) exhibited no labeling, indicating the specificity of the AQP9 antibodies. Immunoblotting revealed a predominant band of 28 kDa in membranes of total rat liver, epididymis, testes, spleen, and brain. Preabsorption with the immunizing peptides eliminated the labeling. Immunohistochemistry showed strong anti-AQP9 labeling in liver hepatocytes. The labeling was strongest at the sinusoidal surface, and there was little intracellular labeling. Immunoelectron microscopy revealed that the labeling was associated with the plasma membrane of the hepatocytes. In testes Leydig cells exhibited anti-AQP9 labeling, and in epididymis, the stereocilia of the ciliated cells (principal cells) exhibited significant labeling, whereas there was no labeling of the nonciliated cells (basal cells). This was confirmed by immunoelectron microscopy. In spleen strong labeling of cells was observed of leukocytes in the red pulp, whereas there was no labeling of cells in the white pulp. In rat brain, AQP9 immunolabeling was confined to ependymal cells lining the ventricles and to the tanycytes of the mediobasal hypothalamus. Antibody preabsorbed with the immunizing peptide revealed no labeling. In conclusion, AQP9 proteins is strongly expressed in rat liver, testes, epididymis, spleen, and brain.

References (11)

  • K. Ishibashi et al.

    Biochem. Biophys. Res. Commun.

    (1998)
  • H. Tsukaguchi et al.

    J. Biol. Chem.

    (1998)
  • T. Ma et al.

    Biochem. Biophys. Res. Commun.

    (1997)
  • S.B. Ko et al.

    Biochem. Mol. Biol. Int.

    (1999)
  • A. Matsubara et al.

    J. Neurosci.

    (1996)
There are more references available in the full text version of this article.

Cited by (0)

Abbreviations used: AQP, aquaporin; BSA, bovine serum albumin; CNS, central nervous system; ECL, enhanced chemiluminescence system; EDTA, ethylenediaminetetraacetic acid; ICV, intracerebroventricular; PAGE, polyacrylamide gel electrophoresis; SDS, sodium dodecyl sulfate; SSC, sodium chloride sodium citrate; TRIS, tris(hydroxymethyl)-aminomethane; TBE, tris borate EDTA.

1

M.-L.E. and Z.V. contributed equally to this work.

2

To whom correspondence should be addressed at Department of Cell Biology, Institute of Anatomy, University of Aarhus, DK-8000 Aarhus, Denmark. Fax: +45 86198664. E-mail: [email protected].

View full text