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This Article Full Text Full Text (PDF) All Versions of this Article: 294/3/R1033    most recent 00516.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Tresguerres, M. Articles by Luquet, C. M. Search for Related Content PubMed PubMed Citation Articles by Tresguerres, M. Articles by Luquet, C. M.

COMPARATIVE AND EVOLUTIONARY PHYSIOLOGY

Regulation of ion transport by pH and [HCO₃^–] in isolated gills of the crab Neohelice (Chasmagnathus) granulata

¹Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada; ²Department of Pharmacology, Weill Medical College of Cornell University, New York, New York; ³Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina; ⁴Departamento Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina; and ⁵Asentamiento Universitario San Martín de los Andes, Neuquén, Argentina

Submitted 16 July 2007 ; accepted in final form 7 January 2008

Posterior isolated gills of Neohelice (Chasmagnathus) granulatus were symmetrically perfused with hemolymph-like saline of varying [HCO₃^–] and pH. Elevating [HCO₃^–] in the saline from 2.5 to 12.5 mmol/l (pH 7.75 in both cases) induced a significant increase in the transepithelial potential difference (V_te), a measure of ion transport. The elevation in [HCO₃^–] also induced a switch from acid secretion (–43.7 ± 22.5 µequiv·kg^–1·h^–1) in controls to base secretion (84.7 ± 14.4 µequiv·kg^–1·h^–1). The HCO₃^–-induced V_te increase was inhibited by basolateral acetazolamide (200 µmol/l), amiloride (1 mmol/l), and ouabain (5 mmol/l) but not by bafilomycin (100 nmol/l). The V_te response to HCO₃^– did not take place in Cl^–-free conditions; however, it was unaffected by apical SITS (2 mmol/l) or DIDS (1 mmol/l). A decrease in pH from 7.75 to 7.45 pH units in the perfusate also induced a significant increase in V_te, which was matched by a net increase in acid secretion of 67.8 ± 18.4 µequiv kg^–1 h^–1. This stimulation was sensitive to basolateral acetazolamide, bafilomycin, DIDS, and Na⁺-free conditions, but it still took place in Cl^–-free saline. Therefore, the cellular response to low pH is different from the HCO₃^–-stimulated response. We also report V-H⁺-ATPase- and Na⁺-K⁺-ATPase-like immunoreactivity in gill sections for the first time in this crab. Our results suggest that carbonic anhydrase (CA), basolateral Na⁺/H⁺ exchangers and Na⁺-K⁺-ATPase and apical anion exchangers participate in the HCO₃^–-stimulated response, while CA, apical V-H⁺-ATPase and basolateral HCO₃^–-dependent cotransporters mediate the response to low pH.

acid/base regulation; HCO₃^– secretion; V-H⁺-ATPase; carbonic anhydrase; electrogenic Na⁺/H⁺ exchanger; amiloride; acetazolamide; bafilomycin