Immunolocalisation of aquaporin 3 in the gill and the gastrointestinal tract of the European eel Anguilla anguilla (L.).
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.
Lignot
Jean-H
JH
School of Biology, University of St Andrews, St Andrews, Fife KY16 9TS, Scotland.
Cutler
Christopher P
CP
Hazon
Neil
N
Cramb
Gordon
G
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
D020346:Aquaporins; D051400:Aquaporin 3