title: Cryohydrocytosis: increased activity of cation carriers in red cells from a patient with a band 3 mutation.
abstract: BACKGROUND
  Cryohydrocytosis is an inherited dominant hemolytic anemia characterized by mutations in a transmembrane segment of the anion exchanger (band 3 protein). Transfection experiments performed in Xenopus oocytes suggested that these mutations may convert the anion exchanger into a non-selective cation channel. The present study was performed to characterize so far unexplored ion transport pathways that may render erythrocytes of a single cryohydrocytosis patient cation-leaky.
  
  
  METHODS
  Cold-induced changes in cell volume were monitored using ektacytometry and density gradient centrifugation. Kinetics, temperature and inhibitor-dependence of the cation and water movements in the cryohydrocytosis patient's erythrocytes were studied using radioactive tracers and flame photometry. Response of the membrane potential of the patient's erythrocyte membrane to the presence of ionophores and blockers of anion and cation channels was assessed.
  
  
  RESULTS
  In the cold, the cryohydrocytosis patient's erythrocytes swelled in KCl-containing, but not in NaCl-containing or KNO(3)-containing media indicating that volume changes were mediated by an anion-coupled cation transporter. In NaCl-containing medium the net HOE-642-sensitive Na(+)/K(+) exchange prevailed, whereas in KCl-containing medium swelling was mediated by a chloride-dependent K(+) uptake. Unidirectional K(+) influx measurements showed that the patient's cells have abnormally high activities of the cation-proton exchanger and the K(+),Cl(-) co-transporter, which can account for the observed net movements of cations. Finally, neither chloride nor cation conductance in the patient's erythrocytes differed from that of healthy donors. Conclusions These results suggest that cross-talk between the mutated band 3 and other transporters might increase the cation permeability in cryohydrocytosis.
authors.affiliation: Zurich Center for Integrative, Human Physiology, University of Zurich, Winterthurerstr 260, CH 8057 Zurich, Switzerland. annab@access.uzh.ch
authors.forename: Anna
authors.initials: A
authors.lastname: Bogdanova
authors.forename: Jeroen S
authors.initials: JS
authors.lastname: Goede
authors.forename: Erwin
authors.initials: E
authors.lastname: Weiss
authors.forename: Nikolay
authors.initials: N
authors.lastname: Bogdanov
authors.forename: Poul
authors.initials: P
authors.lastname: Bennekou
authors.forename: Ingolf
authors.initials: I
authors.lastname: Bernhardt
authors.forename: Hans U
authors.initials: HU
authors.lastname: Lutz
mesh_terms: D000328:Adult; D000743:Anemia, Hemolytic / Q000097:blood / Q000235:genetics* / Q000378:metabolism*; D001457:Anion Exchange Protein 1, Erythrocyte / Q000235:genetics*; D002412:Cations / Q000097:blood / Q000378:metabolism; D003080:Cold Temperature; D004907:Erythrocyte Deformability; D004912:Erythrocytes / Q000378:metabolism; D006801:Humans; D017136:Ion Transport; D008297:Male; D009154:Mutation; D011188:Potassium / Q000097:blood / Q000378:metabolism; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism*
chemical_list: D001457:Anion Exchange Protein 1, Erythrocyte; D002412:Cations; D028021:Sodium-Potassium-Chloride Symporters; D011188:Potassium