title: Mechanism of the increase in cation permeability of human erythrocytes in low-chloride media. Involvement of the anion transport protein capnophorin.
abstract: When human erythrocytes are suspended in low-Cl- media (with sucrose replacing Cl-), there is a large increase in both the net efflux and permeability of K+. A substantial portion (greater than 70% with Cl- less than 12.5 mM) of this K+ efflux is inhibited by the anion exchange inhibitor DIDS (4,4'-diisothiocyanostilbene-2,2'-disulfonic acid). This inhibition cannot be explained as an effect of DIDS on net Cl- permeability (Pcl) and membrane potential, but rather represents a direct effect on the K+ permeability. When cells are reacted with DIDS for different times, the inhibition of K+ efflux parallels that of Cl- exchange, which strongly indicates that the band 3 anion exchange protein (capnophorin) mediates the net K+ flux. Since a noncompetitive inhibitor of anion exchange, niflumic acid, has no effect on net K+ efflux, the net K+ flow does not seem to involve the band 3 conformational change that mediates anion exchange. The data suggest that in low-Cl- media, the anion selectivity of capnophorin decreases so that it can act as a very low-conductivity channel for cations. Na+ and Rb+, as well as K+, can utilize this pathway.
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D001457:Anion Exchange Protein 1, Erythrocyte / Q000502:physiology*; D002352:Carrier Proteins / Q000502:physiology*; D002463:Cell Membrane Permeability / Q000187:drug effects; D002712:Chlorides / Q000502:physiology*; D004910:Erythrocyte Membrane / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D009761:Nystatin / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism
chemical_list: D001457:Anion Exchange Protein 1, Erythrocyte; D002352:Carrier Proteins; D002712:Chlorides; D009761:Nystatin; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D012964:Sodium; D012413:Rubidium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium