Relationship of net chloride flow across the human erythrocyte membrane to the anion exchange mechanism.

Abstract

The parallel effects of the anion transport inhibitor DIDS (4,4'-diisothiocyanostilbene-2,2'-disulfonate) on net chloride flow and on chloride exchange suggest that a major portion of net chloride flow takes place through the anion exchange system . The "slippage" model postulates that the rate of net any change in transport site conformation such as normally occurs during the anion exchange process . This model is successful in predicting that the anion exchange inhibitor NAP-taurine, which binds to the modifer site and inhibits the conformational change, has less effect on net chloride flow than on chloride exchange .

Dipyridamole inhibits sickling-induced cation fluxes in sickle red blood cells

“…4,10,11 It is known that anion-transport inhibitors, 23,25 including dipyridamole, 18,21 block Ca ϩϩ -activated K ϩ fluxes since the extremely rapid, electrogenic K ϩ movements via the Ca ϩϩ -activated channel are limited by conductive anion permeability, mediated predominately by the anion exchanger. 26 We compared the dipyridamole dose response of the Ca ϩϩ -activated K ϩ flux and the sickling-induced Na ϩ influx by parallel measurements of the 2 fluxes in aliquots of the same cell suspension under similar conditions of hematocrit and drug exposure as shown in Figure 6. Ca ϩϩ -activated K ϩ efflux was measured in SS RBCs incubated with ionophore A23187 in the presence of Ca ϩϩ at 2% hematocrit.…”

The role of anion transport in the passive movement of lead across the human red cell membrane.

“…Cl-> Br-> F-> l-> NO3- (Obaid et al 1980 Exchange of a neutral species for an anion is unprecedented. The anion-transport system can bring about the net movement of anions, but it has been suggested that this occurs by 'tunneling' of the anion, rather than exchange of the anion with an unloaded site (Knauf, Law & Marchant, 1983;Frdhlich, 1984). Glycine can be carried by the red cell anion system (Ellory, Jones & Young, 1981).…”

Patch-Clamp Analysis of Membrane Transport in Erythrocytes

“…This conductive part of chloride permeability ensures a dissipation of chloride gradient across red cell membrane: the membrane potential is clamped at the equilibrium potential for chloride (-12mV) ensuring that Band 3 never has to fight against a chloride gradient to transport bicarbonate ions across red cell membrane. Before the use of patch clamp, both components were frequently attributed to Band 3 protein activity, the electrogenic part resulting from either slippage in the exchange mechanism (Kaplan et al, 1983;Knauf et al, 1977), or tunneling (Frohlich, 1984;Knauf et al, 1983).…”