Low pH Induced Shape Changes and Vesiculation of Human Erythrocytes (original) (raw)
Related papers
A possible physical mechanism of red blood cell vesiculation obtained by incubation at high pH
Journal of Biomechanics, 1997
The membrane of human red blood cells is essentially composed of two parts, the lipid bilayer and the membrane skeleton that interacts with the lipid bilayer. The normal resting shape of the red blood cells at physiological pH 7.4 is the discocyte. However, at alkaline pHK11 the shape of red blood cells is composed of a spherical parent cell and large spherical daughter vesicles. The daughter vesicles may be free or connected to the parent cell by a narrow neck. In this paper we show that the shapes of red blood cells at pHK11 correspond to some of the calculated shapes of a closed lipid bilayer having an extreme area difference between the outer and the inner monolayer. Therefore, it is suggested that the observed shapes of the red blood cells at pHK11 are a consequence of the abolishment of the skeleton-bilayer interactions at this pH.
The Effect of pH on the Volume, Density and Shape of Erythrocytes and Thymic Lymphocytes
British Journal of Haematology, 1968
Erythrocytes increase in volume, decrease in density and become more spherical as the pH of isotonic media decreases over the range 9.4-4.8. Swelling is rapid, reversible, occurs in a wide range of media and is independent ofgas exchange; there is strong indirect evidence that it is independent of metabolic activity. The swelling is largely the result of entry of anions in the cell as the pH falls, in accordance with the degree of ionization of haemoglobin and Gibbs-Donnan equilibria. Human erythrocytes show a complex response to the anion uptake, fail to act as perfect osmometers and 'resist' swelling in isotonic solutions. Rat erythrocytes differ, and swell to the extent predicted from their anion uptake. 'Studies of gas and electrolyte equilibria in the blood. V. Factors controlling the electrolyte and water distribution in the blood.']. biol. Chem., 56, 765. WHITTAM, R. (1964). Transport and Di@usion in Red Blood Cells.
Membrane skeleton and red blood cell vesiculation at low pH
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1998
Shapes of red blood cells at low pH were studied theoretically. It is assumed that the equilibrium shape of the red blood cell corresponds to the minimum of its membrane elastic energy which consists of the bending energy and relative stretching energy of the bilayer, the stretching energy of the skeleton and the interaction energy between the skeleton and the bilayer. It is shown that the aggregation of the skeleton at low pH can cause the red blood cell shape transformation from the stomatocytic shape to the cell shape composed of a spherical parent cell having the bilayer completely underlaid with the skeleton and spherical daughter vesicles without the skeleton. q 1998 Elsevier Science B.V.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1999
HCl-induced lysis of mammalian erythrocytes, pretreated with DIDS, which is a specific inhibitor of the anion transport in their membranes, was markedly delayed. After acidification of a suspension of DIDS-inhibited cells, hemolysis was initiated by addition of a protonophore (Na-salicylate) at any moment chosen by will. These findings revealed that low-pH hemolysis depended on the rate of the transfer of acid equivalents into cytosole. Erythrocyte acid resistance was studied in a group of mammals and found to be inversely related to the rate of monovalent anion exchange in membranes which supported the above observations. In human erythrocytes, the critical level of cytosole acidification was found to be about pH 5.7 by measuring the acid equivalent absorbed by cells prior to hemolysis. HCl-induced hemolysis was also studied in human erythrocyte ghosts resealed with one-sixth of the initial hemoglobin content of cells. During the prelytic interval the ghosts suspended in isotonic NaCl/sucrose media shrunk, indicating an increase in ion permeability. The increase in prelytic permeability and hemolysis were strongly delayed in ghosts prepared from DIDS-treated cells, suggesting a uniform mechanism of lysing in cells and their ghosts. The prelytic increase in ion permeability was measured by the corresponding rate of ghost shrinkage and was found to be pH-dependent, with a high value below pH 3.4 and a very low one above pH 4.0. Compared to cells, the prelytic barrier impairment in ghosts had more mild character although it required greater concentration of cytosolic H. While finally complete, hemolysis of cells was strongly delayed in the presence of catalase (500^1500 U/ml) and superoxide dismutase (200^600 U/ml) in hemolytic media. In conclusion, the acid-induced hemolysis could be associated with an oxidative injury of membranes, mainly triggered by the entry of acid equivalents into the cytosole.
pH-dependent behaviour of erythrocyte membrane elevations
Cell Biology International Reports, 1978
Freeze-etch electron microscopy of human erythrocytes from heparinized normal blood reveals membrane elevations. These elevations disappear at low pH values and reappear under normal pH conditions in vitro, both in the absence and the presence of plasma. This pH-dependent behaviour is discussed as an intrinsic membrane event.
Charge-independent effects of drugs on erythrocyte morphology
Biochemical Pharmacology, 1986
The effects of ~hlorp~m~ne, tetracaine, i~domethacin, barbitone and benzyl alcohol on human erytbrocyte shape have been examined. Cationic and anionic drugs produced stomatocy~es and echinocytes respectively as expected for cells in isotonic saline. Particular attention has been directed here to some features of drug induced morphology change which are independent of the charge of the drug. It was found that (i) the direction (increase or decrease) of the extent of morphological change as temperature was increased from 20 to 37", (ii) the exposure time for maximum shape change (O-2 min), and (iii) the time course of cell morphology (O-30 min) were different for similarly charged drugs. The influence of low concentrations of the drugs on the thermal fragmentation patterns of the cells has been determined. A single index has been derived which allows comparison of the morphological
Biochemical Pharmacology, 1985
The influence of the anionic drugs indomethacin, barbitone, salicylate and the cationic drugs chlorpromazine and tetracaine on the morphology of human erythrocytes suspended in solutions of different chloride concentration (thus altering cell membrane potential) and constant osmolality, has been examined. As expected, the anionic and cationic drugs produced echinocytes and stomatocytes respectively in 145 mM NaCl. The cationic drugs induced fewer stomatocytes in 60 mM chloride than in 145 mM chloride at 37". Tetracaine induced echinocytes in 60 mM chloride at 20". Indomethacin and barbitone produced echinocytes in 145 mM chloride and stomatocytes in 60 mM chloride. Salicylate no longer produced echinocytes when the chloride concentration was reduced. Cells exposed to salicylate in 60mM chloride were less cupped than the control cells. We suggest that the distribution of the charged form of the drug across the membrane is in equilibrium with the distribution of chloride ions. Changes in the intracellular drug concentration when the extracellular chloride is varied could then account for the observed shape changes in a manner which is consistent with the bilayer couple hypothesis for drug-membrane interactions.
Echinocyte formation induced by potential changes of human red blood cells
The Journal of Membrane Biology, 1982
In isotonic 30 mM NaCl-saccharose solution, human red blood cells with intact membrane and normal inside ionic content (C-state) indicate a transmembrane potential between +30mV (at pH 7.4) and +46mV (at pH 5.1). After treatment with amphotericin B or nystatin as ionophores, a Donnan equilibrium (D-state) will be reached with the same potential at pH 5.1 but a sharp drop down to-20 mV will occur at pH 7.4. Concerning the erythrocyte shape at these states, a stomatocyteechinocyte transformation takes place, in correlation with the potential shift. Stomatocytes formed at A~> +25mV, echinocytes at A ~,< +25 inV. At potentials lower than +5 mV, no further effect can be observed. This process is reversible. Neuraminidase treatment as well as outside EDTA do not influence this process significantly. Human serum albumin in concentrations of 2 ~ stabilizes the stomatocytes.
Colloids and Surfaces B: Biointerfaces, 2004
This study represents an attempt to achieve a better understanding of the stomatocyte-echinocyte transition in the shape of red blood cells. We determined experimentally the index of cell shape at various ionic strengths and osmolarities for native and trypsin-treated human erythrocytes. For every given composition of the outer phase, we calculated the ionic strength in the cells and the transmembrane electric potential using a known theoretical model. Next, we described theoretically the electric double layers formed on both sides of the cell membrane, and derived expressions for the tensions of the two membrane leaflets. Taking into account that the cell-shape index depends on the tension difference between the two leaflets, we fitted the experimental data with the constructed physicochemical model. The model, which agrees well with the experiment, indicates that the tension difference between the two leaflets is governed by the different adsorptions of counterions at the two membrane surfaces, rather than by the direct contribution of the electric double layers to the membrane tension. Thus, with the rise of the ionic strength, the counterion adsorption increases stronger at the outer leaflet, whose stretching surface pressure becomes greater, and whose area expands relative to that of the inner leaflet. Hence, there is no contradiction between the bilayer-couple hypothesis and the electric double layer theory, if the latter is upgraded to account for the effect of counterion-adsorption on the membrane tension. The developed quantitative model can be applied to predict the shape index of cells upon a stomatocyte-discocyte-echinocyte transformation at varying composition of the outer medium.