title: Immunolocalisation of aquaporin 3 in the gill and the gastrointestinal tract of the European eel Anguilla anguilla (L.).
abstract: The expression of a putative water channel protein, aquaporin 3 (AQP-3), has been localised within branchial and intestinal tissues from the 'silver' life stage of the European eel Anguilla anguilla, using a specific polyclonal antibody directed against the C-terminal of the amino acid sequence. Western blots using the AQP-3 antiserum identified the presence of a major immunoreactive protein of 24 kDa in extracts of gills from both freshwater (FW) and 3 week seawater (SW)-acclimated eels. SW acclimation induced a 65 % reduction in AQP-3 protein abundance in the gill extracts. AQP-3 immunoreactivity was apparent throughout the branchial epithelium from both FW and SW-acclimated fish, but especially so within the chloride cells, which also stained heavily with specific antisera for the beta-subunit of the Na, K-ATPase. AQP-3 immunoreactivity not only colocalised with Na, K-ATPase within the basolateral tubular network but also stained the apical regions of the chloride cell where Na, K-ATPase was absent. Although there were no obvious differences in expression between the chloride cells of FW and SW-acclimated fish, considerably higher intensities of immunoreactivity were apparent near the periphery of the non-chloride cells of FW fish, especially within cells forming the base of the primary filaments and the branchial arch. AQP-3 immunoreactivity was also detected in intra-epithelial macrophage-like cells within the intestine of FW and SW-acclimated eels and in the mucous cells of the rectal epithelium of SW-acclimated fish. These results suggest that AQP-3 may play an important functional role in osmoregulation the teleostean gill but is unlikely to be responsible for the increases in intestinal water absorption that occur following SW acclimation.
authors.affiliation: School of Biology, University of St Andrews, St Andrews, Fife KY16 9TS, Scotland.
authors.forename: Jean-H
authors.initials: JH
authors.lastname: Lignot
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Cutler
authors.forename: Neil
authors.initials: N
authors.lastname: Hazon
authors.forename: Gordon
authors.initials: G
authors.lastname: Cramb
mesh_terms: D000064:Acclimatization / Q000502:physiology; D000811:Anguilla / Q000033:anatomy & histology / Q000378:metabolism* / Q000502:physiology; D000818:Animals; D051400:Aquaporin 3; D020346:Aquaporins / Q000378:metabolism*; D004064:Digestive System / Q000378:metabolism* / Q000648:ultrastructure; D005618:Fresh Water; D005880:Gills / Q000378:metabolism* / Q000648:ultrastructure; D007150:Immunohistochemistry; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D016253:Microscopy, Immunoelectron; D012623:Seawater; D014882:Water-Electrolyte Balance
chemical_list: D020346:Aquaporins; D051400:Aquaporin 3