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pubmed:abstractText |
1. The permeability of the human erythrocyte to anions has been measured under conditions of net charge transfer: for Cl(-) and HCO(3) (-) ions, at 37 degrees C, this permeability is 5 orders of magnitude too small to account for the rate of the electroneutral anion exchange which is responsible for the chloride, or Hamburger, shift.2. The method is an indirect one in which the ionophore, valinomycin, is used to increase the erythrocyte K(+) permeability: in the absence of permeant cation externally, the rate of the resulting K(+) efflux may be limited by the slowness of the accompanying anion efflux, allowing the true anion permeability to be estimated.3. The average Cl(-) permeability estimated in ACD-stored erythrocytes (seven experiments) and erythrocytes from fresh blood (two experiments) was 2.1 x 10(-8) cm/sec at 37 degrees C and pH 7.4: this may also be expressed as a Cl(-) conductance of about 1.0 x 10(-5) Omega(-1) cm(-2). The apparent activation energy for net efflux of Cl(-) was found to be 3.9 kJ/mole (16.4 kcal/mole).4. In fresh cells, the ratios of Cl(-), HCO(3) (-), Br(-) and I(-) permeabilities (or conductances) were 1:0.8:1.5:5. The three halide ions follow Eisenman's Sequence I, representing a binding site of low field strength.
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