Aquaporin 8 (AQP8) Intestinal mRNA Expression Increases in Response to Salinity Acclimation in Yellow and Silver European Eels (Anguilla anguilla)

Document Type

Article

Publication Date

6-2009

Publication Title

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology

DOI

10.1016/j.cbpa.2009.04.047

ISSN

1095-6433

Abstract

Work in this lab and elsewhere has shown that when euryhaline eels are acclimated from freshwater to seawater, the expression of (the water-selective) aquaporin 1 (AQP1) water channel mRNA and protein is upregulated (up to 25-fold; Martinez et al., Am.J.Physiol.288: R1733–43 2005). Similar up-regulation can also be induced (up to 50-fold) by infusion of the ‘seawater' acting hormone, cortisol, into freshwater fish. Immunohistochemical studies show that the main location of AQP1 expression in surface cell epithelia, is in the rectal region, and the posterior intestine surrounding the sphincter that delineates the intestine from the rectum. These data suggested a potential osmoregulatory role for aquaporins in trans-epithelial water uptake from the intestinal lumen following seawater acclimation, however, for the transcellular water uptake pathway to be playing a significant role in intestinal water absorption, further water transport proteins, such as other aquaporins, have to be involved. Studies have shown that Aquaporin 8 (AQP8) is one such candidate. Data show 1) that AQP8 is only expressed at a significant level in the intestine, that 2) its mRNA expression increases in response to salinity acclimation and 3) preliminary data suggest that unlike AQP1, the increase in AQP8 mRNA expression is not under the control of the hormone, cortisol.

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