Characterization of Aquaporin 8 Isoform Expression in Eel (emAnguilla sp./em) Intestine

Euryhaline eels are placed under severe osmotic stress when they migrate from freshwater to seawater during their lifecycle. In seawater, the animals drink to maintain equilibrium; to obtain water to replace continual losses occurring due to osmosis across permeable body surfaces. A significant increase in the intestine’s capacity to absorb water from imbibed fluid consequently occurs and this may involve upregulation of aquaporin water channels. Studies using quantitative polymerase chain reaction or Northern blotting have shown increases in aquaporin 8 and 8b isoform mRNA levels in intestinal segments following seawater acclimation of eels. Custom-made isoform-specific polyclonal antibodies have been raised against aquaporin 8 and 8b, and these show intracellular staining in intestine surface epithelial cells. Additionally, there are indications of a lateral plasma membrane localization of aquaporin 8 and 8b isoforms in rectal surface epithelial cells, suggesting a role for aquaporin 8 and 8b isoforms in water absorption mechanisms. Results of Western blot experiments may also be presented. This work was supported by a National Science Foundation grant IOS 0844818. J. Walsh and M. Kuijpers are supported by Georgia Southern University, Chandler research scholarships. Summer research on this project was performed at the Mount Desert Island Biological Laboratory, ME.