title: Bicarbonate-chloride exchange in gill plasma membranes of blue crab.
abstract: The uptake of chloride was studied in gill plasma membrane vesicles from low-salinity-adapted blue crabs (Callinectes sapidus). Cl- uptake was not Na+ dependent. However, when a HCO-3 gradient (in greater than out) was imposed across the membrane, a transient overshoot of about 2.5-fold was produced. Approximately 90% of the Cl- uptake reflected entry into the osmotically active intravesicular space. Cl- itself, nitrate, hydroxyl, and sulfite could substitute for HCO-3. The HCO-3/Cl- exchange process appeared to saturate at higher concentrations of either HCO-3 or Cl-. The apparent Km for Cl- was 15 mM. HCO-3-dependent Cl- uptake was significantly inhibited by 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid and thiocyanate but not by amiloride, furosemide, or ouabain. Alterations in membrane potential had no effect on Cl- uptake. Addition of Cl- or HCO-3 to the external medium also accelerated efflux of 36Cl- and H14CO-3 from preloaded vesicles. These results indicate that the uptake of Cl- by the crab gill plasma membrane is a carrier-mediated Na+-independent anion exchange process.
mesh_terms: D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000086:Acetazolamide / Q000494:pharmacology; D000818:Animals; D000838:Anions / Q000494:pharmacology; D001639:Bicarbonates / Q000378:metabolism*; D003386:Brachyura / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism*; D003956:Dialysis / Q000379:methods; D005880:Gills / Q000378:metabolism* / Q000648:ultrastructure; D007474:Ion Exchange; D007700:Kinetics; D008564:Membrane Potentials; D013861:Thiocyanates / Q000494:pharmacology
chemical_list: D000838:Anions; D001639:Bicarbonates; D002712:Chlorides; D013861:Thiocyanates; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D000086:Acetazolamide; C031760:thiocyanate