NaCl uptake by the branchial epithelium in freshwater teleost fish: an immunological approach to ion-transport protein localization.
Teleost fishes, living in fresh water, engage in active ion uptake to maintain ion homeostasis. Current models for NaCl uptake involve Na(+) uptake via an apical amiloride-sensitive epithelial Na(+) channel (ENaC), energized by an apical vacuolar-type proton pump (V-ATPase) or alternatively by an amiloride-sensitive Na(+)/H(+) exchange (NHE) protein, and apical Cl(-) uptake mediated by an electroneutral, SITS-sensitive Cl(-)/HCO(3-) anion-exchange protein. Using non-homologous antibodies, we have determined the cellular distributions of these ion-transport proteins to test the predicted models. Na(+)/K(+)-ATPase was used as a cellular marker for differentiating branchial epithelium mitochondria-rich (MR) cells from pavement cells. In both the freshwater tilapia (Oreochromis mossambicus) and rainbow trout (Oncorhynchus mykiss), V-ATPase and ENaC-like immunoreactivity co-localized to pavement cells, although apical labelling was also found in MR cells in the trout. In the freshwater tilapia, apical anion-exchanger-like immunoreactivity is found in the MR cells. Thus, a freshwater-type MR chloride cell exists in teleost fishes. The NHE-like immunoreactivity is associated with the accessory cell type and with a small population of pavement cells in tilapia.
Wilson
J M
JM
Department of Zoology, University of British Columbia, Vancouver, Canada V6T 1Z4. wilson_jm@cimar.org
Laurent
P
P
Tufts
B L
BL
Benos
D J
DJ
Donowitz
M
M
Vogl
A W
AW
Randall
D J
DJ
D000818:Animals; D017920:Antiporters / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D027963:Chloride-Bicarbonate Antiporters; D004847:Epithelial Cells / Q000378:metabolism / Q000648:ultrastructure; D005880:Gills / Q000378:metabolism / Q000648:ultrastructure; D007150:Immunohistochemistry; D017136:Ion Transport; D016253:Microscopy, Immunoelectron; D008954:Models, Biological; D017686:Oncorhynchus mykiss / Q000033:anatomy & histology / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000378:metabolism; D015222:Sodium Channels / Q000378:metabolism; D012965:Sodium Chloride / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013045:Species Specificity; D017210:Tilapia / Q000033:anatomy & histology / Q000378:metabolism*; D025262:Vacuolar Proton-Translocating ATPases
D017920:Antiporters; D002352:Carrier Proteins; D027963:Chloride-Bicarbonate Antiporters; D015222:Sodium Channels; D017923:Sodium-Hydrogen Exchangers; D012965:Sodium Chloride; D025262:Vacuolar Proton-Translocating ATPases; D006180:Proton-Translocating ATPases; D000254:Sodium-Potassium-Exchanging ATPase