Intestinal carbonic anhydrase, bicarbonate, and proton carriers play a role in the acclimation of rainbow trout to seawater

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology integrative and comparative physiology, 2007-11, Vol.293 (5), p.R2099-R2111
• Main Authors: Grosell, Martin, Gilmour, Katie M, Perry, Steven F
• Format: Article
• Language: English
• Subjects: Adaptation, Physiological - genetics; Adaptation, Physiological - physiology; Adsorption; Animals; Bicarbonates - metabolism; Brackish; Carbonic Anhydrases - genetics; Carbonic Anhydrases - metabolism; Cells; Epithelium - metabolism; Freshwater; Gene Expression - physiology; Immunohistochemistry; In Vitro Techniques; Intestines - enzymology; Intestines - metabolism; Marine; Oncorhynchus mykiss; Oncorhynchus mykiss - physiology; Proteins; Proton-Translocating ATPases - genetics; Proton-Translocating ATPases - metabolism; Protons; Seawater; Sodium-Bicarbonate Symporters - metabolism; Sodium-Hydrogen Exchanger 3; Sodium-Hydrogen Exchangers - metabolism; Sodium-Potassium-Exchanging ATPase - metabolism; Trout; Water - metabolism; Water-Electrolyte Balance - genetics; Water-Electrolyte Balance - physiology
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.00156.2007

1 Rosensteil School of Marine Atmospheric Sciences, University of Miami, Florida; and 2 University of Ottawa, Ottawa, Ontario, Canada Submitted 2 March 2007 ; accepted in final form 28 August 2007 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. water absorption; HCO 3 – secretion; intestinal H + transport; tCAIV; tCAc Address for reprint requests and other correspondence: M. Grosell, RSMAS, Univ. of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149-1098 (e-mail: mgrosell{at}rsmas.miami.edu )