Expression and immunolocalization of aquaporin-7 in rat gastrointestinal tract

Umberto Laforenza, Giulia Gastaldi, Monica Grazioli, Emanuela Cova, Simona Tritto, Alide Faelli, Giuseppe Calamita, Ulderico Ventura

Research output: Contribution to journalArticlepeer-review

Abstract

Background information. In the gastrointestinal tract of mammals, water can either be secreted with digestive juices or absorbed by the small and large intestine. Transcellular water movement can be mediated by the transmembrane protein family of AQPs (aquaporins), as has also been recently identified in the gastrointestinal tract. However, the localization, expression and functioning of AQPs in the gastrointestinal tract have not been completely characterized. For the present study, we investigated: (1) the expression of AQP7 in some portions of rat gastrointestinal tract by semiquantitative reverse transcriptase-PCR and by immunoblotting and (2) the cellular and subcellular localization of AQP7 by immunohistochemistry. Results. AQP7 mRNA and proteins were highly expressed in the small intestine, weakly in the caecum, colon and rectum and were absent in the stomach. Immunoblotting analysis using rat gastrointestinal tract membrane fractions showed two major bands corresponding to a molecular mass of approx. 34 and 40 kDa for the AQP7 protein. No bands were observed when the anti-AQP7 antibody was preadsorbed with the immunizing peptide. Immunohistochemistry revealed strong AQP7 labelling in the surface epithelial cells of duodenum, jejunum, ileum, caecum, colon and rectum, whereas weak or no labelling was observed in the crypt cells. The labelling was manifest particularly in the apical membrane but intracellular staining was also observed. Conclusions. The results indicate that AQP7 is present in the small and large intestine. The higher expression of AQP7 protein at the apical pole of the superficial epithelial cells suggests its involvement in rapid fluid movement through the villus epithelium.

Original languageEnglish
Pages (from-to)605-613
Number of pages9
JournalBiology of the cell / under the auspices of the European Cell Biology Organization
Volume97
Issue number8
DOIs
Publication statusPublished - Aug 2005

Keywords

  • Apical membrane
  • AQP7 protein
  • Immunohistochemistry
  • RT-PCR
  • Water channel

ASJC Scopus subject areas

  • Cell Biology

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