Volume regulation and KCl cotransport in reticulocyte populations of sickle and normal red blood cells

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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Volume Regulation in Red Blood Cells

The Biology of Hagfishes ◽

10.1007/978-94-011-5834-3_19 ◽

1998 ◽

pp. 300-306

Author(s):

Niels Dohn ◽

Hans Malte

Keyword(s):

Red Blood Cells ◽

Blood Cells ◽

Volume Regulation

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Active and passive Ca movements in dog red blood cells and resealed ghosts

AJP Cell Physiology ◽

10.1152/ajpcell.1979.237.1.c10 ◽

1979 ◽

Vol 237 (1) ◽

pp. C10-C16 ◽

Cited By ~ 24

Author(s):

J. C. Parker

Keyword(s):

Body Temperature ◽

Red Blood Cells ◽

Cell Volume ◽

Blood Cells ◽

Volume Regulation ◽

Cell Volume Regulation ◽

Low Ph ◽

Coupling Ratio ◽

Cell Shrinkage ◽

Resealed Ghosts

Dog red blood cells accumulate Ca rapidly when deprived of substrate or cooled to 5 degrees C. The latter effect is reversible as the cells are rewarmed to body temperature. Resealed ghosts extrude Ca, provided ATP is incorporated in them. Passive fluxes of Ca are stimulated by Na on the opposite side of the membrane, consistent with a model for Ca-Na countertransport. Quinidine, cell shrinkage, and low pH--all known to suppress net Ca influx--have no accelerating effect on Ca efflux, thus validating earlier conclusions about the variability of the coupling ratio for Ca-Na exchange. The significance of these findings for cell volume regulation is discussed.

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Cellular volume regulation in salinity stressed molluscs: The response ofNoetia ponderosa (Arcidae) red blood cells to osmotic variation

Journal of Comparative Physiology B ◽

10.1007/bf00691562 ◽

1980 ◽

Vol 138 (4) ◽

pp. 283-289 ◽

Cited By ~ 30

Author(s):

Lynn M. Amende ◽

Sidney K. Pierce

Keyword(s):

Red Blood Cells ◽

Blood Cells ◽

Volume Regulation ◽

Cellular Volume

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Activation of electroneutral K flux in Amphiuma red blood cells by N-ethylmaleimide. Distinction between K/H exchange and KCl cotransport.

The Journal of General Physiology ◽

10.1085/jgp.90.2.209 ◽

1987 ◽

Vol 90 (2) ◽

pp. 209-227 ◽

Cited By ~ 19

Author(s):

J S Adorante ◽

P M Cala

Keyword(s):

Red Blood Cells ◽

Blood Cells ◽

Driving Force ◽

Flow Analysis ◽

Cell Swelling ◽

Direct Effects ◽

Kcl Cotransport ◽

Thermodynamic Forces ◽

Exchange Flux ◽

Stimulation Of

Exposure of Amphiuma red blood cells to millimolar concentrations of N-ethylmaleimide (NEM) resulted in net K loss. In order to determine whether net K loss was conductive or was by electroneutral K/H exchange or KCl cotransport, studies were performed evaluating K flux in terms of the thermodynamic forces to which K flux by the above pathways should couple. The direction and magnitude of the NEM-induced net K flux did not correspond with the direction and magnitude of the forces relevant to K conductance or electroneutral KCl cotransport. Both the magnitude and direction of the NEM-activated K flux responded to the driving force for K/H exchange. We therefore conclude that NEM-induced K loss, like that by osmotically swollen Amphiuma red blood cells, is by an electroneutral K/H exchanger. In addition to the above studies, we evaluated the kinetic behavior of the volume- and NEM-induced K/H exchange flux pathways in media where Cl was replaced by SCN, NO3, para-aminohippurate (PAH), or gluconate. The anion replacement studies did not permit a distinction between K/H exchange and KCl cotransport, since, depending upon the anion used as a Cl replacement, partial inhibition or stimulation of volume-activated K/H exchange fluxes was observed. In contrast, all anions used were stimulatory to the NEM-induced K loss. Since, on the basis of force-flow analysis, both volume-and NEM-induced K loss are K/H exchange, it was necessary to reevaluate assumptions (i.e., anions serve as substrates and therefore probe the translocation step) associated with the use of anion replacement as a means of flux route identification. When viewed together with the force-flow studies, the Cl replacement studies suggest that anion effects upon K/H exchange are indirect. The different anions appear to alter mechanisms that couple NEM exposure and cell swelling to the activation of K/H exchange, as opposed to exerting direct effects upon K and H translocation.

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Several cation transporters and volume regulation in high-K dog red blood cells

AJP Cell Physiology ◽

10.1152/ajpcell.1991.260.3.c589 ◽

1991 ◽

Vol 260 (3) ◽

pp. C589-C597 ◽

Cited By ~ 24

Author(s):

H. Fujise ◽

I. Yamada ◽

M. Masuda ◽

Y. Miyazawa ◽

E. Ogawa ◽

...

Keyword(s):

Red Blood Cells ◽

Blood Cells ◽

Volume Regulation ◽

Cation Composition ◽

Influx Rate ◽

Physiological Conditions ◽

High K ◽

Dependent Transport ◽

Low K ◽

K Transport

Normal dog red blood cells lack the Na-K pump, and their cation composition is low K and high Na (LK). Recently, a dog was found with red blood cells containing high K and low Na concentrations (HK) due to the existence of the Na-K pump. In the present study, cation transport and volume regulation in HK cells were compared with those of LK cells. HK cells showed not only Rb influx through a Na-K pump, but also Rb influx through a Cl-dependent K transporter. The Rb influx rate through the Na-K pump was 0.65-1.44 mmol.l cells-1.h-1 in Cl and 1.75-2.24 mmol.l cells-1.h-1 in NO3, in HK cells, but only trace activities are found in LK cells. In HK cells, the Rb influx rate through Cl-dependent K transport was 0.36-0.96 mmol.l cells-1.h-1, and it was enhanced in swollen cells but vanished in shrunken cells. In LK cells, the transport was evident only in swollen cells. The original volume of swollen HK cells was restored by water extrusion promoted by Cl-dependent transport. The Na-Ca exchange transporter, which works as a volume regulator in LK cells, functioned in HK cells only when they were loaded with Na. Hence, the exchange transporter is latent in HK cells under physiological conditions. Moreover, the exchange transporter could restore the cell volume in swollen and Na-loaded HK cells. However, the volume in HK cells was still larger than that in LK cells, while the Na-Ca exchange transporter was working.(ABSTRACT TRUNCATED AT 250 WORDS)

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

Journal of Experimental Zoology ◽

10.1002/jez.1401990307 ◽

1977 ◽

Vol 199 (3) ◽

pp. 339-344 ◽

Cited By ~ 13

Author(s):

Peter M. Cala

Keyword(s):

Membrane Potential ◽

Red Blood Cells ◽

Blood Cells ◽

Volume Regulation

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Deoxygenation of sickle red blood cells stimulates KCl cotransport without affecting Na+/H+exchange

AJP Cell Physiology ◽

10.1152/ajpcell.1998.274.6.c1466 ◽

1998 ◽

Vol 274 (6) ◽

pp. C1466-C1475 ◽

Cited By ~ 25

Author(s):

C. H. Joiner ◽

M. Jiang ◽

H. Fathallah ◽

F. Giraud ◽

R. S. Franco

Keyword(s):

Red Blood Cells ◽

Blood Cells ◽

Low Density ◽

Cell Shrinkage ◽

Kcl Cotransport ◽

A 23187 ◽

Dependent Component ◽

Sickle Red Blood Cells ◽

Exchange Activity ◽

External K

KCl cotransport activated by swelling of sickle red blood cells (SS RBC) is inhibited by deoxygenation. Yet recent studies found a Cl−-dependent increase in sickle reticulocyte density with cyclic deoxygenation. This study sought to demonstrate cotransporter stimulation by deoxygenation of SS RBC in isotonic media with normal pH. Low-density SS RBC exhibited a Cl−-dependent component of the deoxygenation-induced net K+efflux, which was blocked by two inhibitors of KCl cotransport, [(dihydroindenyl)oxy]alkanoic acid and okadaic acid. Cl−-dependent K+efflux stimulated by deoxygenation was enhanced 2.5-fold by clamping of cellular Mg2+at the level in oxygenated cells using ionophore A-23187. Incubating cells in high external K+or Rb+minimized inhibition of KCl cotransport by internal Mg2+, and under these conditions deoxygenation markedly stimulated KCl cotransport in the absence of ionophore. Activation of KCl cotransport by deoxygenation of SS RBC in isotonic media at normal pH is consistent with the generalized dephosphorylation of membrane proteins induced by deoxygenation and activation of the cotransporter by a dephosphorylation mechanism. Na+/H+exchange activity, known to be modulated by cytosolic Ca2+elevation and cell shrinkage, remained silent under deoxygenation conditions.

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Volume regulation by Amphiuma red blood cells. The membrane potential and its implications regarding the nature of the ion-flux pathways.

The Journal of General Physiology ◽

10.1085/jgp.76.6.683 ◽

1980 ◽

Vol 76 (6) ◽

pp. 683-708 ◽

Cited By ~ 246

Author(s):

P M Cala

Keyword(s):

Membrane Potential ◽

Alkali Metal ◽

Red Blood Cells ◽

Cell Volume ◽

Blood Cells ◽

Volume Regulation ◽

Regulatory Volume Decrease ◽

Cell Volume Regulation ◽

Ion Flux ◽

Regulatory Response

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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