Expression and localization of aquaporin water channels in human exocrine pancreas

  • Home
  • Expression and localization of aquaporin water channels in human exocrine pancreas

Puerto de la Cruz, Tenerife (2003) J Physiol 548P, P39

Poster Communications: Expression and localization of aquaporin water channels in human exocrine pancreas

B. Burghardt*, M.-L. Elkj¾r†, T.-H. Kwon‡, G.Z. Rácz*, G. Varga*¤, M.C. Steward¦ and S Nielsen†

*Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary, †The Water and Salt Research Center, University of Aarhus, Denmark, ‡Department of Physiology, Dongguk University School of Medicine, Korea, ¤Department of Oral Biology, Semmelweis University, Budapest, Hungary and ¦School of Biological Sciences, University of Manchester, UK

View other abstracts by:

The exocrine pancreas secretes large volumes of isotonic, bicarbonate-rich fluid, much of which originates from the ductal system. Since the role of aquaporin (AQP) water channels in this process is unknown, we have investigated the expression and localization of known AQP isoforms in normal human pancreas and in pancreatic cell lines of ductal origin (Capan-1, Capan-2 and HPAF).

RT-PCR was performed with isoform-specific primers on RNA extracted from tissue samples obtained from patients undergoing surgery who had previously given consent according to local procedures. Immunohistochemistry was performed on paraffin sections using affinity-purified antibodies and peroxidase-linked or fluorescent secondary antibodies.

Messenger RNAs for AQP1, -3, -4, -5 and -8 were detected in normal pancreas by RT-PCR. The ductal cell lines expressed AQP3, -4 and -5 but lacked AQP1 and AQP8. Immunohistochemistry of normal pancreas revealed that AQP1 is strongly expressed in the centro-acinar cells and in both the apical and basolateral domains of the intercalated and intralobular duct epithelia. AQP1 expression declined with distance along the small interlobular ducts and was not detectable in the larger interlobular ducts. This is in contrast to the rat pancreas where AQP1 is found mainly in the interlobular ducts (Ko et al. 2002). AQP3 and AQP4 were not detectable in human pancreas by immunohistochemistry despite the positive RT-PCR results. AQP5 was observed at the apical membrane of the intercalated duct cells and also in duct-associated mucoid glands. AQP8 was confined to the apical pole of the acinar cells, as previously observed in the rat pancreas (Hurley et al. 2001). Using immunofluorescence, both AQP1 and AQP5 were co-localized with CFTR at the apical membrane of the intercalated duct cells.

We conclude that AQP1 and AQP5 are strongly expressed in the intercalated ducts of the human pancreas, and that their distribution correlates closely with that of CFTR, a marker of ductal electrolyte secretion. This suggests that fluid secretion occurs predominantly in the terminal branches of the ductal tree and that both AQP1 and AQP5 may be involved.

This study was supported by Danish National Research Foundation, the Hungarian Ministry of Social Welfare and the Wellcome Trust.

Where applicable, experiments conform with Society ethical requirements.

Menu Menu Search

Site search

Filter

Content Type