Inhibition of anion transport in human red blood cell : effect on the electrophoretic velocity

The electrophoretic mobility exhibited by the human red blood cells (RBC), under electric field, depends on: 1) the intensity of the applied electric field, 2) the shape and the net surface charge density of the cell, 3) the characteristics of the suspending medium (pH, ionic strength, viscosity and osmolarity). Negative cell surface charge is due to both membrane glycolipids and glycoproteins. We studied the influence of some inhibitors of anion exchange [phenylglyoxal (PG) and three PG derivatives: 4-hydroxy-3-nitrophenylglyoxal (HNPG), 3-methoxyphenylglyoxal (3MOPG) and 4-methoxyphenylgyoxal (4MOPG)] on electrophoretic mobility. The experiments were performed in an horizontal cylindrical capillary by the microscope method at room temperature and physiological pH; the ionic strength was 0.262 mol/l. After treatment with the inhibitors RBCs showed a reduced electrophoretic mobility: -16.7% by PG (5 mM), -14.7, -17.6% and -18.4% by HNPG (2 mM), 3MOPG(2mM) and 4MOPG (10 mM). The surface electrical charge density was calculated by two models: assuming the RBC to be spherical or using a flat plate model. All inhibitors reduced the surface electrical charge density: -18.7 and -21.2 by PG, -14.6 and -16.9 by HNPG, -16.9 and -19.2 by 3MOPG, -19.4 and -21.8 by 4MOPG respectively. The major role of inhibitors probably lies in their capability to react with arginine of Band 3 masking the glycoprotein charges and thus reducing the negative surface electrical charge. In agreement with the characteristics of the inhibitory action on the anion exchange, we found a completely reversible HNPG reduction of electrophoretic mobility while it was not the case for PG, 3MOPG and 4MOPG reduction.