Volume regulation by Flounder red blood cells: The role of the membrane potential

After osmotic perturbation, the red blood cells of Amphiuma exhibited a volume-regulatory response that returned cell volume back to or toward control values. After osmotic swelling, cell-volume regulation (regulatory volume decrease; RVD) resulted from net cellular loss of K, Cl, and osmotically obliged H2O. In contrast, the volume-regulatory response to osmotic shrinkage (regulatory volume increase; RVI) was characterized by net cellular uptake of Na, Cl, and H2O. The net K and Na fluxes characteristic of RVD and RVI are increased by 1-2 orders of magnitude above those observed in studies of volume-static control cells. The cell membrane potential of volume-regulating and volume-static cells was measured by impalement with glass microelectrodes. The information gained from the electrical and ion-flux studies led to the conclusion that the ion fluxes responsible for cell-volume regulation proceed via electrically silent pathways. Furthermore, it was observed that Na fluxes during RVI were profoundly sensitive to medium [HCO3] and that during RVI the medium becomes more acid, whereas alkaline shifts in the suspension medium accompany RVD. The experimental observations are explained by a model featuring obligatorily coupled alkali metal-H and Cl-HCO3 exchangers. The anion- and cation-exchange pathways are separate and distinct yet functionally coupled via the net flux of H. As a result of the operation of such pathways, net alkali metal, Cl, and H2O fluxes proceed in the same direction, whereas H and HCO3 fluxes are cyclic. Data also are presented that suggest that the ion-flux pathways responsible for cell-volume regulation are not activated by changes in cell volume per se but by some event associated with osmotic perturbation, such as changes in intracellular pH.

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Role of chloride in potassium transport through a K-Cl cotransport system in human red blood cells

AJP Cell Physiology ◽

10.1152/ajpcell.1989.256.5.c994 ◽

1989 ◽

Vol 256 (5) ◽

pp. C994-C1003 ◽

Cited By ~ 55

Author(s):

C. Brugnara ◽

T. Van Ha ◽

D. C. Tosteson

Keyword(s):

Membrane Potential ◽

Red Blood Cells ◽

Blood Cells ◽

Normal Subjects ◽

Similar Data ◽

Human Red Blood Cells ◽

Dense Fraction ◽

Cotransport System ◽

Low K

In this paper, we report experiments demonstrating the coupling of Cl and K movements in a volume-dependent K-Cl cotransport system in human red blood cells. We show that an outwardly directed Cl gradient can promote net K efflux against an inwardly directed K gradient at constant membrane potential. Red blood cell membrane potential was kept constant by using anions that are not transported through the K-Cl cotransport system but that are more permeable than Cl (NO3 and SCN). Under these conditions, when the activities of band 3 (capnophorin)-mediated anion exchange and of the carbonic anhydrase have been inhibited, it is possible to maintain a Cl gradient at constant membrane potential. Similar data were obtained in human red blood cells (least dense fraction from normal subjects and whole blood from patients with homozygous hemoglobin S disease), in rabbit red blood cells, and in low-K sheep red blood cells. These data confirm that the volume-dependent Cl-dependent K movement in these cells operates through coupled K-Cl cotransport.

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Role of Adhesion Molecules and Vascular Endothelium in the Pathogenesis of Sickle Cell Disease

Hematology ◽

10.1182/asheducation-2007.1.84 ◽

2007 ◽

Vol 2007 (1) ◽

pp. 84-90 ◽

Cited By ~ 27

Author(s):

Marilyn J. Telen

Keyword(s):

Sickle Cell Disease ◽

Red Blood Cells ◽

Adhesion Molecules ◽

Sickle Cell ◽

Vascular Endothelium ◽

Blood Cells ◽

Cell Disease ◽

Adhesive Interactions ◽

Lines Of Evidence

AbstractA number of lines of evidence now support the hypothesis that vaso-occlusion and several of the sequelae of sickle cell disease (SCD) arise, at least in part, from adhesive interactions of sickle red blood cells, leukocytes, and the endothelium. Both experimental and genetic evidence provide support for the importance of these interactions. It is likely that future therapies for SCD might target one or more of these interactions.

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Role of Calcium in Phosphatidylserine Externalisation in Red Blood Cells from Sickle Cell Patients

Anemia ◽

10.1155/2011/379894 ◽

2011 ◽

Vol 2011 ◽

pp. 1-8 ◽

Cited By ~ 11

Author(s):

Erwin Weiss ◽

David Charles Rees ◽

John Stanley Gibson

Keyword(s):

Red Blood Cells ◽

Sickle Cell ◽

Blood Cells ◽

Phosphatidylserine Exposure ◽

Channel Inhibition ◽

Cation Conductance ◽

Gardos Channel ◽

Cation Permeability

Phosphatidylserine exposure occurs in red blood cells (RBCs) from sickle cell disease (SCD) patients and is increased by deoxygenation. The mechanisms responsible remain unclear. RBCs from SCD patients also have elevated cation permeability, and, in particular, a deoxygenation-induced cation conductance which mediates entry, providing an obvious link with phosphatidylserine exposure. The role of was investigated using FITC-labelled annexin. Results confirmed high phosphatidylserine exposure in RBCs from SCD patients increasing upon deoxygenation. When deoxygenated, phosphatidylserine exposure was further elevated as extracellular [] was increased. This effect was inhibited by dipyridamole, intracellular chelation, and Gardos channel inhibition. Phosphatidylserine exposure was reduced in high saline. levels required to elicit phosphatidylserine exposure were in the low micromolar range. Findings are consistent with entry through the deoxygenation-induced pathway (), activating the Gardos channel. [] required for phosphatidylserine scrambling are in the range achievablein vivo.

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Minimal volume regulation after shrinkage of red blood cells from five species of reptiles

Comparative Biochemistry and Physiology Part A Molecular & Integrative Physiology ◽

10.1016/j.cbpa.2008.03.002 ◽

2008 ◽

Vol 150 (1) ◽

pp. 46-51 ◽

Cited By ~ 3

Author(s):

Karina Kristensen ◽

Michael Berenbrink ◽

Pia Koldkjær ◽

Augusto Abe ◽

Tobias Wang

Keyword(s):

Red Blood Cells ◽

Blood Cells ◽

Volume Regulation ◽

Minimal Volume

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Mechanism by which cyanine dyes measure membrane potential in red blood cells and phosphatidylcholine vesicles

Biochemistry ◽

10.1021/bi00713a022 ◽

1974 ◽

Vol 13 (16) ◽

pp. 3315-3330 ◽

Cited By ~ 711

Author(s):

Peter J. Sims ◽

Alan S. Waggoner ◽

Chao-Huei Wang ◽

Joseph F. Hoffman

Keyword(s):

Membrane Potential ◽

Red Blood Cells ◽

Blood Cells ◽

Cyanine Dyes ◽

Measure Membrane Potential

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Volume regulation by flounder red blood cells in anisotonic media

The Journal of General Physiology ◽

10.1085/jgp.69.5.537 ◽

1977 ◽

Vol 69 (5) ◽

pp. 537-552 ◽

Cited By ~ 64

Author(s):

PM Cala

Keyword(s):

Red Blood Cells ◽

Cell Volume ◽

Water Flow ◽

Blood Cells ◽

Volume Regulation ◽

Control Cell ◽

Regulatory Volume Decrease ◽

Electrochemical Gradient ◽

Osmotic Swelling ◽

Inorganic Cation

The nucleated high K, low Na red blood cells of the winter flounder demonstrated a volume regulatory response subsequent to osmotic swelling or shrinkage. During volume regulation the net water flow was secondary to net inorganic cation flux. Volume regulation the net water flow was secondary to net inorganic cation flux. Volume regulation after osmotic swelling is referred to as regulatory volume decrease (RVD) and was characterized by net K and water loss. Since the electrochemical gradient for K is directed out of the cell there is no need to invoke active processes to explain RVD. When osmotically shrunken, the flounder erythrocyte demonstrated a regulatory volume increase (RVI) back toward control cell volume. The water movements characteristic of RVI were a consequence of net cellular NaCl and KCl uptake with Na accounting for 75 percent of the increase in intracellular cation content. Since the Na electrochemical gradient is directed into the cell, net Na uptake was the result of Na flux via dissipative pathways. The addition of 10(-4)M ouabain to suspensions of flounder erythrocytes was without effect upon net water movements during volume regulation. The presence of ouabain did however lead to a decreased ration of intracellular K:Na. Analysis of net Na and K fluxes in the presence and absence of ouabain led to the conclusion that Na and K fluxes via both conservative and dissipative pathways are increased in response to osmotic swelling or shrinkage. In addition, the Na and K flux rate through both pump and leak pathways decreased in a parallel fashion as cell volume was regulated. Taken as a whole, the Na and K movements through the flounder erythrocyte membrane demonstrated a functional dependence during volume regulation.

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