Electron spin resonance studies on the inorganic-anion-transport system of the human red blood cell. Binding of a disulfonatostilbene spin label (NDS-TEMPO) and inhibition of anion transport.
The disulfonatostilbene spin label, NDS-TEMPO, was synthesized (purity over 96%) and the binding of the spin label to human red-cell ghosts was studied. NDS-TEMPO is readily absorbed to the membrane surface. Both pretreatment of the ghosts with FDNB and DIDS and the presence of DNDS completely prevent the binding of NDS-TEMPO to red-cell ghosts. Chloride and sulfate competitively inhibit the binding of NDS-TEMPO. Conversely, NDS-TEMPO is a strong, competitive inhibitor of chloride and of sulfate transport. The dissociation constants of NDS-TEMPO from the ESR studies were in the range 1.0-2.0 microM (pH 7.6, 20 degrees C). The inhibition constants of NDS-TEMPO as obtained from the flux experiments were in the range 0.5-2.5 microM (pH 7.3, 25 degrees C). The close accordance of the NDS-TEMPO dissociation constants from the ESR studies with the NDS-TEMPO inhibition constants from the flux measurements indicate a specific labeling of the inorganic-anion-transport system.
D000838:Anions; D001692:Biological Transport; D002458:Cell Fractionation; D002712:Chlorides / Q000097:blood*; D003497:Cyclic N-Oxides / Q000494:pharmacology*; D004578:Electron Spin Resonance Spectroscopy; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D013113:Spin Labels / Q000494:pharmacology*; D013431:Sulfates / Q000097:blood*
D000838:Anions; D002712:Chlorides; D003497:Cyclic N-Oxides; D013113:Spin Labels; D013431:Sulfates; C038825:N-4-(2,2,6,6-tetramethyl-1-oxyl)piperidinyl-N'-4-(4'-nitro-2,2'-stilbenedisulfonic acid)thiourea