Relationship between the shape and the membrane potential of human red blood cells

Abstract

Microscopic observations of isotonic suspensions of human red blood cells demonstrate that cell shape is unaltered when the transmembrane electrical potential, or Em, is set in the range -85 to + 10 mV with valinomycin at varied external K+, or Ko X Em was measured with the fluorescent potentiometric indicator, diS-C3(5), as calibrated by a delta pH method. Repeating Glaser's experiments in which echinocytosis was attributed to hyperpolarization, we found that at low ionic strength the pH-dependent effects of amphotericin B appear to be unrelated to Em. The effects of increased intracellular Ca2+, or Cac, on echinocytosis and on Em are separable. With Ca ionophore A23187 half-maximal echinocytosis occurs at greater Cao than that which induces the half-maximal hyperpolarization associated with Ca-induced K+ conductance (Gardos effect). Thus, cells hyperpolarized by increased Cac remain discoidal when Ca is below the threshold for echinocytosis. With A23187 and higher Cao, extensive echinocytosis occurs in cells which are either hyperpolarized or at their resting potential. The Ca-activation curve for echinocytosis is left-shifted by low Ko, a new observation consistent with increased DIDS-sensitive uptake of 45Ca by hyperpolarized cells. These results support the following conclusions: (1) the shape and membrane potential of human red blood cells are independent under the conditions studied; (2) in cells treated with A23187, the Gardos effect facilitates echinocytosis by increasing Cac.

On the mechanism of stomatocyte–echinocyte transformations of red blood cells: experiment and theoretical model

“…1) upon variation of the electrolyte concentration [1][2][3][4][5][6][7], increase of the medium's pH [7][8][9][10][11][12], addition of amphiphiles and other agents [1,[13][14][15][16][17][18], and changes in temperature [19,20]. A general correlation was found between the erythrocyte shape and the transmembrane electric potential [21][22][23][24][25]. The effect of pH and other agents could be also attributed to their influence on the transmembrane potential [25].…”

A Possible Molecular Mechanism Governing Human Erythrocyte Shape

“…These data clearly demon-strate that neither shrinkage nor pH i , but only the transmembrane potential correlates with shape. Gedde et al (1997b) point out, as Bifano et al (1984) already did, that "ionophores have independent shape effect." This is true for large concentrations and was published by us for high concentrations of valinomycin (Glaser et al, 1991).…”

A hypothesis of the disc–sphere transformation of the erythrocytes between glass surfaces and of related observations

“…This disc-sphere transformation, which was referred as the glass effect as it was believed to be different from those induced by surface-active substances, is the oldest one known and was attributed to a modification of the surface tension in the absence of other explanations. It has been the object of investigations over the years (Gough, 1924;Furchgott, 1940;Furchgott and Ponder, 1940;Ponder, 1948;Tompkins, 1954;Brown, 1956;Trotter, 1956;Ponder and Ponder, 1962;Bessis and Prenant, 1972;Mehta, 1983;Bifano et al, 1984;Eriksson, 1990;Deuticke, 2003). However, it remains yet to be satisfactorily explained although significant progress has been achieved.…”

“…Indeed, they inhibit the Band 3 anion transport activity, and several of them inhibit the Band 3 anion transport activity and alter the shape concomitantly. The slowly transported Band 3 substrates arsenate, iodide, nitrate, oxalate and vanadate (Ponder, 1948;Vives-Corrons et al, 1981;Tajima, 1986;Eriksson, 1990;Winski and Carter, 1998), and the specific Band 3 anion transport inhibitors dipyridamole, DIDS (4,4 0 -diisothiocyanotostilbene-2, 2 0 -disulfonic acid) and DNDS (4,4 0 -dinitrostilbene-2,2 0 -disulfonic acid) are echinocytogenic (Bifano et al, 1984;Hoefner et al, 1994;Gimsa and Ried, 1995;Schwarz et al, 1999). Gimsa and Ried (1995) have also suggested that the erythrocyte shape transformations produced by pH change are caused by a Band 3 conformational change since they occur too rapidly to be explained by a redistribution of the phospholipids of the lipid bilayer and that the membrane skeleton is unable by itself to maintain the shape, owing to its high flexibility.…”