Volume-dependent K+ transport in rabbit red blood cells comparison with oxygenated human SS cells

1989 ◽  
Vol 257 (1) ◽  
pp. C114-C121 ◽  
Author(s):  
N. al-Rohil ◽  
M. L. Jennings
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Cell Volume Regulation ◽  
Sulfhydryl Group ◽  
Cell Swelling ◽  
Inhibitory Potency ◽  
Ph Optimum ◽  
The Relationship ◽  
Low K ◽  
K Transport

In this study the volume-dependent or N-ethylmaleimide (NEM)-stimulated, ouabain-insensitive K+ influx and efflux were measured with the tracer 86Rb+ in rabbit red blood cells. The purpose of the work was to examine the rabbit as a potential model for cell volume regulation in human SS red blood cells and also to investigate the relationship between the NEM-reactive sulfhydryl group(s) and the signal by which cell swelling activates the transport. Ouabain-resistant K+ efflux and influx increase nearly threefold in cells swollen hypotonically by 15%. Pretreatment with 2 mM NEM stimulates efflux 5-fold and influx 10-fold (each measured in an isotonic medium). The ouabain-resistant K+ efflux was dependent on the major anion in the medium. The anion dependence of K+ efflux in swollen or NEM-stimulated cells was as follows: Br- greater than Cl- much greater than NO3- = acetate. The magnitudes of both the swelling- and the NEM-stimulated fluxes are much higher in young cells (density separated but excluding reticulocytes) than in older cells. Swelling- or NEM-stimulated K+ efflux in rabbit red blood cells was inhibited 50% by 1 mM furosemide, and the inhibitory potency of furosemide was enhanced by extracellular K+, as is known to be true for human AA and low-K+ sheep red blood cells. The swelling-stimulated flux in both rabbit and human SS cells has a pH optimum at approximately 7.4. We conclude that rabbit red blood cells are a good model for swelling-stimulated K+ transport in human SS cells.(ABSTRACT TRUNCATED AT 250 WORDS)

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

1991 ◽  
Vol 260 (3) ◽  
pp. C589-C597 ◽  
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)

Thiol-dependent passive K+-Cl- transport in sheep red blood cells. V. Dependence on metabolism

1983 ◽  
Vol 245 (5) ◽  
pp. C445-C448 ◽  
Author(s):  
P. K. Lauf
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Inorganic Phosphate ◽  
Transport Systems ◽  
Thiol Groups ◽  
Sheep Red Blood Cells ◽  
Cl Transport ◽  
Free Media ◽  
Low K ◽  
K Transport

Measurement of ouabain-insensitive K+ efflux and Rb+ influx in low-K+ sheep red blood cells with artificially altered cellular ATP levels revealed that Cl--dependent K+ transport was activated by N-ethylmaleimide (NEM) in cells with ATP concentrations above 0.5 mM. Depletion of ATP by starvation at 37 degrees C either in glucose-free media for 16 h or in 2-deoxy-D-glucose-containing media for 4 h completely abolished the response of K+-Cl-transport to NEM but did not reduce the basal Cl--dependent K+ flux. On repletion of cellular ATP by a second incubation in media containing glucose, inosine, and inorganic phosphate, the NEM-stimulated K+ (Rb+) flux reappeared. The magnitude of flux reactivation varied directly and monotonically with the ATP level. The data constitute the first unequivocal evidence for a reversible ATP dependence of thiol groups functionally involved in the thiol-dependent K+-Cl- transporter, suggesting that thiol-dependent and volume-sensitive K+-Cl- transport systems are operationally different.

Loop diuretic and anion modification of NEM-induced K transport in human red blood cells

1990 ◽  
Vol 258 (4) ◽  
pp. C622-C629 ◽  
Author(s):  
L. R. Berkowitz
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Loop Diuretic ◽  
Sulfhydryl Group ◽  
Loop Diuretics ◽  
Human Red Blood Cells ◽  
Anion Substitution ◽  
Cellular Target ◽  
K Transport ◽  
Permeant Anion

The thioalkylating agent N-ethylmaleimide (NEM) causes ouabain-insensitive K loss from human red blood cells. This K loss is inhibited when intracellular Cl is replaced by another permeant anion or when loop diuretics are placed in the incubation medium after NEM exposure. In this report, we have tested the possibility that Cl replacement or loop diuretics not only influence the transport of K induced by NEM but also the interaction of NEM with its target sulfhydryl group. This possibility was examined by replacing intracellular Cl or exposing the cells to loop diuretics before NEM exposure, then measuring K loss in a Cl medium free of loop diuretics. We found that such pretreatment with either Cl substitution or loop diuretics stimulated, rather than inhibited, NEM-induced K loss. This enhancement was not additive in that the increase in K loss induced by anion substitution was not increased further when loop diuretics were also present. These data suggest that anion substitution and loop diuretics enhance the interaction of NEM with its cellular target but inhibit the K loss induced by NEM.

Activation by N-ethylmaleimide of a latent K+-Cl- flux in human red blood cells

1984 ◽  
Vol 246 (5) ◽  
pp. C385-C390 ◽  
Author(s):  
P. K. Lauf ◽  
N. C. Adragna ◽  
R. P. Garay
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Sulfhydryl Group ◽  
Maximum Velocity ◽  
Coupled Transport ◽  
Human Red Blood Cells ◽  
Low Concentrations ◽  
Reactive Groups ◽  
High Concentrations ◽  
K Transport

Twenty to fifty percent of the ouabain-insensitive Na+ and K+ fluxes in human red blood cells are mediated by Cl(-) -dependent coupled transport (cotransport). In this paper we report on the effect of the sulfhydryl group reagent N-ethylmaleimide (NEM) on Cl(-) -dependent ouabain-insensitive Na+ and K+ fluxes in human red blood cells. We found that NEM altered Na+ -K+ cotransport and activated a latent Cl(-) -dependent K+ transport mode normally apparently silent. This conclusion was based on the following observations. 1) At low concentrations (0.25 mM) NEM abolished the bumetanide-sensitive Na+ efflux and had no effect, even at a 10-fold higher concentration, on the bumetanide-sensitive K+ efflux. 2) At concentrations above 0.1 mM, NEM stimulated Cl(-) -dependent K+ efflux that was only partially inhibited by high concentrations of bumetanide or furosemide. In experiments using Rb+ as a K+ analogue, NEM activated Rb+ influx by stimulating the maximum velocity and lowering the apparent external cation affinity. The data suggest the presence of chemically reactive groups in human red blood cells for both Cl(-) -dependent K+ transport activated by NEM and Cl(-) -dependent coupled Na+-K+ movements.

Stimulation of Na+-K+ pump in sheep red blood cells by heteroimmune anti-sheep red cell antibodies

1984 ◽  
Vol 247 (1) ◽  
pp. C120-C123 ◽  
Author(s):  
P. B. Dunham ◽  
B. E. Farquharson ◽  
R. L. Bratcher
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Red Cell ◽  
Sheep Red Blood Cells ◽  
L Cells ◽  
High K ◽  
First Time ◽  
Low K ◽  
K Transport ◽  
Stimulation Of

In the HK-LK polymorphism of sheep red blood cells, alloimmune antiserum against the L antigen on LK cells is known to stimulate the Na+-K+ pump in low K+ (LK) cells, but alloimmune antiserum against the M antigen of high K+ (HK) cells does not. We have shown for the first time that heteroimmune antibodies against sheep red blood cells raised in mice can stimulate the pump. Heteroimmune antibodies against both LK(L) cells and HK(M) cells stimulated active K+ transport in LK cells. Furthermore heteroimmune antibodies against LK(L) cells also stimulated the pump in HK cells. As expected, alloimmune and heteroimmune antibodies acted at different sites in stimulating transport in LK cells.

Na and K Transport in Red Blood Cells

1980 ◽  
pp. 255-272 ◽  
Author(s):  
Philip B. Dunham ◽  
Joseph F. Hoffman
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
K Transport

Volume-responsive sodium movements in dog red blood cells

1983 ◽  
Vol 244 (5) ◽  
pp. C324-C330 ◽  
Author(s):  
J. C. Parker
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Cell Swelling ◽  
Cell Shrinkage ◽  
Ph Change ◽  
Sodium Permeability ◽  
Sodium Gradient ◽  
Sodium Flux ◽  
Sodium Hydrogen Exchanger

As dog red blood cells are shrunken in vitro, their sodium permeability increases progressively. Some new features of this volume-responsive transport process are described. Retardation of sodium movements in shrunken cells occurs when chloride is replaced by the more conductive anions: nitrate or thiocyanate. Micromolar concentrations of amiloride or quinidine inhibit the increment of sodium flux associated with a reduction in cell volume. In the presence of a large outwardly directed sodium gradient, dog red blood cells can progressively alkalinize the medium in which they are suspended. This pH change is stimulated by cell shrinkage, reversed by cell swelling, retarded when chloride is replaced by nitrate or thiocyanate, and inhibited by micromolar concentrations of amiloride or quinidine. The similarities between the shrinkage-associated sodium flux and the alkalinization phenomenon suggest that the mechanism responsible for increased sodium permeability in shrunken cells can be made to operate as a sodium-hydrogen exchanger.

Kinetics of Na-Li exchange in high and low K sheep red blood cells

1989 ◽  
Vol 257 (1) ◽  
pp. C58-C64 ◽  
Author(s):  
K. H. Ryu ◽  
N. C. Adragna ◽  
P. K. Lauf
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Cell Types ◽  
Sheep Red Blood Cells ◽  
High K ◽  
Ping Pong ◽  
Order Of Magnitude ◽  
Low K ◽  
Kinetics Of ◽  
System Operating

The kinetic parameters and transport mechanism of Na-Li exchange were studied in both low K (LK) and high K (HK) sheep red blood cells with cellular Na [( Na]i) and Li concentrations [( Li]i) adjusted by the nystatin technique (Nature New Biol. 244: 47-49, 1973 and J. Physiol. Lond. 283: 177-196, 1978). Maximum velocities (Vm) for Li fluxes and half-activation constants (K1/2) for Li and Na of the Na-Li exchanger were determined. The K1/2 values for both Li and Na appeared to be similar in both cell types, although they were about two to three times lower on the inside than on the outside of the membrane. Furthermore, the K1/2 values for Li were at least an order of magnitude smaller than those for Na, suggesting substantial affinity differences for these two cations. The Vm values for Li fluxes, on the other hand, appear to be lower in HK than in LK cells. When Na and Li fluxes were measured simultaneously, a trans stimulatory effect by Na on Li fluxes was observed. From measurements of Li influx at different concentrations of external Li and different [Na]i, the ratio of the apparent Vm to the apparent external Li affinity was calculated to be independent of [Na]i for both types of sheep red blood cells. Similar trans effects of external Na were observed on Li efflux at varying [Li]i. These results are expected for a system operating by a “ping-pong” mechanism.

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