Regulation of ion transport by pH and [HCO3-] in isolated gills of the crab Neohelice (Chasmagnathus) granulata.
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 (Vte), a measure of ion transport. The elevation in [HCO3-] also induced a switch from acid secretion (-43.7 +/- 22.5 microequiv.kg(-1).h(-1)) in controls to base secretion (84.7 +/- 14.4 microequiv.kg(-1).h(-1)). The HCO3(-)-induced Vte increase was inhibited by basolateral acetazolamide (200 micromol/l), amiloride (1 mmol/l), and ouabain (5 mmol/l) but not by bafilomycin (100 nmol/l). The Vte 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 Vte, which was matched by a net increase in acid secretion of 67.8 +/- 18.4 microequiv 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.
Tresguerres
Martin
M
Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada. mat2031@med.cornell.edu
Parks
Scott K
SK
Sabatini
Sebastian E
SE
Goss
Greg G
GG
Luquet
Carlos M
CM
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology*; D001693:Biological Transport, Active / Q000187:drug effects*; D003386:Brachyura / Q000502:physiology*; D004232:Diuretics / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017952:Ganglia, Invertebrate / Q000502:physiology; D005880:Gills / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007202:Indicators and Reagents; D007477:Ions / Q000378:metabolism; D018942:Macrolides / Q000494:pharmacology; D008564:Membrane Potentials / Q000502:physiology; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D012996:Solutions
D001639:Bicarbonates; D004232:Diuretics; D004791:Enzyme Inhibitors; D007202:Indicators and Reagents; D007477:Ions; D018942:Macrolides; D012996:Solutions; C057620:bafilomycin A; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D006180:Proton-Translocating ATPases; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid