title: Characterization of a phenylglyoxal-sensitive passive Ca2+ permeability in human erythrocytes.
abstract: In viable human erythrocytes, passive downhill entry of Ca2+ through the plasma membrane is opposed by an active extrusion Ca2+-pump mechanism which maintains a free [Ca2+]i approximately 10(-7) M. This passive Ca2+ permeability can be determined reliably in cells with a completely arrested Ca2+ pump, as can be achieved in cells which are both ATP-depleted and vanadate-treated. With this approach, whole-cell preparations from banked human erythrocytes exhibited passive net uptake of Ca2+ that has characteristics of a carrier-mediated process which could be shunted by the addition of the Ca2+ ionophore A23187. Passive Ca2+ uptake was apparently independent of extracellular Na+, K+ or Cl- and was not responsive to a variety of Ca2+ channel entry blockers. However, in the presence of phenylglyoxal, a specific, covalent modifier of arginyl residues, the initial (0 to 60 min) rate of passive Ca2+ uptake was inhibited in a dose-dependent manner. This can be taken in support of a proteinaceous carrier-mediated passive Ca2+ entry mechanism that involves one or several functional arginyl residue(s) and may represent Ca2+ back-diffusion through the arrested Ca2+ translocation pump.
authors.affiliation: Department of Pharmacology and Toxicology, Indiana University School of Medicine, 8600 University Boulevard, Evansville, IN 47712, USA.
authors.forename: B U
authors.initials: BU
authors.lastname: Raess
authors.forename: C E
authors.initials: CE
authors.lastname: Keenan
mesh_terms: D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000493:pharmacokinetics*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002352:Carrier Proteins; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007476:Ionophores / Q000494:pharmacology; D010658:Phenylglyoxal / Q000494:pharmacology*; D011188:Potassium / Q000493:pharmacokinetics; D012964:Sodium / Q000493:pharmacokinetics; D013324:Strontium / Q000378:metabolism; D013696:Temperature
chemical_list: D002121:Calcium Channel Blockers; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D007476:Ionophores; D000001:Calcimycin; D012964:Sodium; D010658:Phenylglyoxal; D011188:Potassium; D002118:Calcium; D013324:Strontium