Shape response of human erythrocytes to altered cell pH

Abstract

Alteration of red blood cell (RBC) pH produces stomatocytosis (at low pH) and echinocytosis (at high pH). Cell shrinkage potentiates high pH echinocytosis, but shrinkage alone does not cause echinocytosis. Mechanisms for these shape changes have not been described. In this study, measured dependence of RBC shape on cell pH was nonlinear, with a broad pH range in which normal discoid shape was maintained. Transbilayer distribution of phosphatidylcholine and phosphatidylserine, measured by back-extraction of radiolabeled lipid, was the same in control and altered pH cells. Possible roles of pH- titratable inner monolayer phospholipids were examined by assessing pH- dependent shape in cells in which their levels had been perturbed. In metabolically depleted cells and calcium-treated cells, which have altered levels of phosphatidic acid, phosphatidylinositol-4-phosphate, and/or phosphatidylinositol-4,5-bisphosphate, low cell pH was stomatocytogenic and high cell pH was echinocytogenic, as in control cells. Thus, neither change in membrane lipid asymmetry nor normal levels of the pH-titratable inner monolayer lipids is necessary for cell pH-mediated shape change.

Echinocyte Shapes: Bending, Stretching, and Shear Determine Spicule Shape and Spacing

“…Some effects are not readily explained by the bilayer-couple mechanism. Weed and Chailley (1972), and Gedde et al (1995Gedde et al ( , 1997aGedde et al ( , 1997bGedde et al ( , 1999 report that RBC shape can be controlled experimentally by varying the external pH, with high pH promoting echinocyte formation and low pH, stomatocyte formation (the effect of proximity to a glass surface in promoting echinocytosis (Furchgott and Ponder, 1940) is probably related to this effect). The mechanism for this effect does not seem to be well established.…”

Plasma Membrane Properties Involved in the Photodynamic Efficacy of Merocyanine 540 and Tetrasulfonated Aluminum Phthalocyanine

“…The transmembrane potential is not the only cellular parameter that depends on the pH of the medium. Upon increasing pH, the shape of the red cells changes from discoid to echinocytic (16) and the volume of the cells decreases (14,15). Also, the surface potential of the red cells is known to depend strongly on the external pH (17).…”

The basis of echinocytosis of the erythrocyte by glucose depletion

“…1,2 However, the process by which ATP depletion leads to the disc-sphere transformation still remains unknown in spite of continuous investigations over the years in which the disc-sphere transformation was generally induced by glucose depletion in buffered saline. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Indeed, it appears unrelated to any of the following: (i) active transport of Na + and K + by ouabain-sensitive membrane Na + , K + -ATPase, opposed by Na + and K + leakage; 4,5 (ii) Ca 2+ uptake, opposed by membrane Ca 2+ -ATPase; 8,13 (iii) formation of lysophosphatidylcholine by a fatty acid deacylation of phosphatidylcholine, opposed by a ATP-dependent fatty acid acylation; 7,23 (iv) phosphorylation state of long and flexible filamentous spectrin, 11,14,18 constituting 60% of the total proteins of the two-dimensional reticulated membrane skeleton; (v) phosphorylation state of the major transmembrane protein Band 3 (AE1), exchanging anion chloride (Cl -), and bicarbonate (HCO 3 -) and binding to filamentous spectrin near its center by intermediary of ankyrin R; 14 (vi) metabolism of phosphatidylinositides, constituting 1-2% of the total membrane phospholipids; 18,21 (vii) contraction of the erythrocyte by myosin present at a relatively low cell number copies (~6000), presumably interacting with actin protofilament cross-linking spectrin at its ends with Band 4.1R binding to glycophorin C. [15][16][17] Moreover, there are several observations suggesting that ATP is not the only determinant of the erythrocyte shape.…”