Intestinal carbonic anhydrase, bicarbonate, and proton carriers play a role in the acclimation of rainbow trout to seawater.
Abrupt transfer of rainbow trout from freshwater to 65% seawater caused transient disturbances in extracellular fluid ionic composition, but homeostasis was reestablished 48 h posttransfer. Intestinal fluid chemistry revealed early onset of drinking and slightly delayed intestinal water absorption that coincided with initiation of NaCl absorption and HCO(3)(-) secretion. Suggestive of involvement in osmoregulation, relative mRNA levels for vacuolar H(+)-ATPase (V-ATPase), Na(+)-K(+)-ATPase, Na(+)/H(+) exchanger 3 (NHE3), Na(+)-HCO(3)(-) cotransporter 1, and two carbonic anhydrase (CA) isoforms [a general cytosolic isoform trout cytoplasmic CA (tCAc) and an extracellular isoform trout membrane-bound CA type IV (tCAIV)], were increased transiently in the intestine following exposure to 65% seawater. Both tCAc and tCAIV proteins were localized to apical regions of the intestinal epithelium and exhibited elevated enzymatic activity after acclimation to 65% seawater. The V-ATPase was localized to both basolateral and apical regions and exhibited a 10-fold increase in enzymatic activity in fish acclimated to 65% seawater, suggesting a role in marine osmoregulation. The intestinal epithelium of rainbow trout acclimated to 65% seawater appears to be capable of both basolateral and apical H(+) extrusion, likely depending on osmoregulatory status and intestinal fluid chemistry.
Grosell
Martin
M
Rosensteil School of Marine Atmospheric Sciences, University of Miami, FL 33149-1098, USA. mgrosell@rsmas.miami.edu
Gilmour
Katie M
KM
Perry
Steven F
SF
D000222:Adaptation, Physiological / Q000235:genetics / Q000502:physiology*; D000327:Adsorption; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D002256:Carbonic Anhydrases / Q000235:genetics / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D015870:Gene Expression / Q000502:physiology; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000201:enzymology*; D017686:Oncorhynchus mykiss / Q000502:physiology*; D006180:Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*; D012623:Seawater; D027982:Sodium-Bicarbonate Symporters / Q000378:metabolism; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D014867:Water / Q000378:metabolism; D014882:Water-Electrolyte Balance / Q000235:genetics / Q000502:physiology*
D001639:Bicarbonates; D027982:Sodium-Bicarbonate Symporters; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D014867:Water; D006180:Proton-Translocating ATPases; D002256:Carbonic Anhydrases; D000254:Sodium-Potassium-Exchanging ATPase