scholarly journals Anion transport in dog, cat, and human red cells. Effects of varying cell volume and Donnan ratio.

1979 ◽  
Vol 74 (3) ◽  
pp. 319-334 ◽  
Author(s):  
V Castranova ◽  
M J Weise ◽  
J F Hoffman
Keyword(s):  
Membrane Potential ◽  
Cell Volume ◽  
Rate Constant ◽  
Rate Constants ◽  
Anion Transport ◽  
Atp Depletion ◽  
Red Cells ◽  
Cell Swelling ◽  
Equilibrium Ratio ◽  
Human Red Cells

Membrane potential and the rate constants for anion self-exchange in dog, cat, and human red blood cells have been shown to vary with cell volume. For dog and cat red cells, the outward rate constants for SO4 and Cl increase while the inward rate constant for SO4 decreases as cells swell or shrink. These changes coincide with the membrane potential becoming more negative as a result of changes in cell volume. Human red cells exhibit a similar change in the rate constants for SO4 and Cl efflux in response to cell swelling, but shrunken cells exhibit a decreased rate constant for SO4 efflux and a more positive membrane potential. Hyperpolarization of shrunken dog and cat red cells is due to a volume-dependent rate constant for SO4 efflux and a more positive membrane potential. Hyperpolarization of shrunken dog and cat red cells is due to a volume-dependent increase in PNa. If this increase in PNa is prevented by ATP depletion or if the outward Na gradient is removed, the response to shrinking is identical to human red cells. These results suggest that the volume dependence of anion permeability may be secondary to changes in the anion equilibrium ratio which in red cells is reflected by the membrane potential. When the membrane potential and cell volume of human red cells were varied independently by a method involving pretreatment with nystatin, it was found that the rate of anion transport (for SO4 and Cl) does not vary with cell volume but rather with membrane potential (anion equilibrium ratio); that is, the rate constant for anion efflux is decreased and that for influx is increased as the membrane potential becomes more positive (internal anion concentration increases) while the opposite is true with membrane hyperpolarization (a fall in internal anion concentration).

scholarly journals Determination of Equivalent Pore Radius for Human Red Cells by Osmotic Pressure Measurement

1960 ◽  
Vol 44 (1) ◽  
pp. 1-18 ◽  
Author(s):  
David A. Goldstein ◽  
A. K. Solomon
Keyword(s):  
Experimental Data ◽  
Pore Radius ◽  
Initial Rate ◽  
Equilibrium Concentration ◽  
External Solution ◽  
Red Cells ◽  
Cell Swelling ◽  
Zero Time ◽  
Human Red Cells

A new method has been developed to measure the equivalent pore radius in cellular membranes, and has been applied to human red cells. When red cells are suddenly introduced into a non-isosmolar concentration of non-lipid-soluble non-electrolyte molecules, water will enter or leave the cell. The rate of cell swelling or shrinking is determined and extrapolated to zero time to give the initial rate of volume change. By suitable adjustment of the concentration of the external solution the initial rate may be brought to zero. The transient equilibrium concentration, determined by interpolation from experimental data, gives a measure of Staverman's reflection coefficient, σ. The zero time method has enabled us to determine σ for nine permeant molecules. σ is directly related to the equivalent pore radius; the experimental data lead to a value of 4.2 Å for the equivalent pore radius in man, in good agreement with the previous figure of 3.5 Å given by Paganelli and Solomon. The zero time method offers a number of advantages over previous methods for determination of this parameter. It requires no measurement of the rate of water entrance into the cell, and is essentially independent of the kinetics of cell swelling. It may be applied to a variety of living cells so that many additional membranes may now be characterized in terms of their equivalent pore radius.

Stretch- and volume-activated channels in isolated proximal tubule cells

1992 ◽  
Vol 262 (5) ◽  
pp. F857-F870 ◽  
Author(s):  
D. Filipovic ◽  
H. Sackin
Keyword(s):  
Membrane Potential ◽  
Proximal Tubule ◽  
Cell Volume ◽  
Regulatory Volume Decrease ◽  
Cell Swelling ◽  
Isolated Cells ◽  
Open Probability ◽  
Proximal Tubule Cells ◽  
Open Time ◽  
Tubule Cells

Apical and basolateral channels were studied in isolated proximal tubule cells of Necturus kidney. Many of these isolated cells maintained their polarity, with clearly delineated apical and basolateral regions. A 20-pS stretch-activated (SA) cation-selective channel was identified at the apical side of these cells. This channel was permeable to Ca, K, and Na but was not significantly gated by either membrane potential or cytosolic Ca. Negative pipette pressure (15 cmH2O) increased the open probability (Po) of this channel from 0.04 +/- 0.02 to 0.26 +/- 0.08 (n = 6). Two types of Ca-independent, mechanosensitive, K-selective (SAK) channels were identified at the basolateral surface of polarized proximal tubule cells, i.e., a 30-pS long-open time (50 +/- 7 ms) channel (n = 9), and a 46-pS short-open time (1.3 +/- 0.7 ms) channel (n = 10). Pipette suction (-12 cmH2O) increased the Po of the short-open time channels from 0.008 to 0.015 and increased the Po of the long-open time channel from 0.03 to 0.19. The effect of swelling was studied with isolated cells suspended at the tip of patch pipettes. A 50% dilution of the bath doubled cell volume, hyperpolarized the membrane potential by 11 +/- 0.7 mV, and increased the Po of the basolateral SAK channels. This was followed by a spontaneous regulatory volume decrease (RVD), repolarization of the membrane potential, and a decrease in Po. In contrast, isosmotic (bath side) replacement of an impermeant anion (methanesulfonate) with a permeant anion (Cl) doubled cell volume in 5 min but without a subsequent RVD. This sustained swelling hyperpolarized the cell potential by 5.5 +/- 0.7 mV (n = 16) and increased the Po of short-open time channel by a factor of 2.3 from 0.03 +/- 0.01 to 0.07 +/- 0.02 (n = 6). The increase in Po was primarily produced by a reduction in the interburst closed time, which decreased from 142 +/- 43 ms in K methanesulfonate to 36 +/- 11 ms in KCl solutions. These results are consistent with the hypothesis that cell swelling activates Ca-independent K channels at the basolateral membrane of renal proximal tubule. Efflux of K through these channels may partially mediate renal cell volume regulation.

Human RhAG ammonia channel is impaired by the Phe65Ser mutation in overhydrated stomatocytic red cells

2012 ◽  
Vol 302 (2) ◽  
pp. C419-C428 ◽  
Author(s):  
Sandrine Genetet ◽  
Pierre Ripoche ◽  
Julien Picot ◽  
Sylvain Bigot ◽  
Jean Delaunay ◽  
...  
Keyword(s):  
Intracellular Ph ◽  
Hemolytic Anemia ◽  
Rate Constant ◽  
Rate Constants ◽  
Flow Analysis ◽  
Red Cells ◽  
Stopped Flow ◽  
Loss Of Function ◽  
Dramatic Decrease ◽  
Time Courses

In red cells, Rh-associated glycoprotein (RhAG) acts as an ammonia channel, as demonstrated by stopped-flow analysis of ghost intracellular pH (pHi) changes. Recently, overhydrated hereditary stomatocytosis (OHSt), a rare dominantly inherited hemolytic anemia, was found to be associated with a mutation (Phe65Ser or Ile61Arg) in RHAG. Ghosts from the erythrocytes of four of the OHSt patients with a Phe65Ser mutation were resealed with a pH-sensitive probe and submitted to ammonium gradients. Alkalinization rate constants, reflecting NH3transport through the channel and NH3diffusion unmediated by RhAG, were deduced from time courses of fluorescence changes. After subtraction of the constant value found for Rhnulllacking RhAG, we observed that alkalinization rate constant values decreased ∼50% in OHSt compared with those of controls. Similar RhAG expression levels were found in control and OHSt. Since half of the expressed RhAG in OHSt most probably corresponds to the mutated form of RhAG, as expected from the OHSt heterozygous status, this dramatic decrease can be therefore related to the loss of function of the Phe65Ser-mutated RhAG monomer.

Competition Between Human Plasma Albumin and Globulins for Estradiol and Sodium Estrone Sulfate

1958 ◽  
Vol 195 (1) ◽  
pp. 81-84 ◽  
Author(s):  
Fritz Bischoff ◽  
John G. Turner ◽  
George Bryson
Keyword(s):  
Human Plasma ◽  
Red Cells ◽  
Albumin Concentration ◽  
Albumin Solution ◽  
Plasma Albumin ◽  
Albumin Fraction ◽  
Estrone Sulfate ◽  
Molar Basis ◽  
Equilibrium Ratio ◽  
Human Red Cells

Equilibrium ratio determinations of estradiol and sodium estrone sulfate distributed between human red cells and solutions of human plasma albumin, fraction IV-1, or fraction IV-4 of Cohn were made at 38°C and ionic strength of 0.155. The albumin contents of the IV-1 and IV-4 fractions were analyzed by 26% sodium sulfate fractionation. When the influence of the albumin in fractions IV-1 and IV-4 was estimated on the basis of the performance of pure albumin solution, the influence of the globulins was small even on a molar basis. The red cell:albumin ratio, using a physiologic albumin concentration, was nearly the same as the endogenous ratio previously obtained for last trimester human red cells: serum. It is concluded that albumin is responsible for 90% or more of the orientation in human plasma of the estrogens studied.

scholarly journals Ionic Mechanisms of Cardiac Cell Swelling Induced by Blocking Na+/K+ Pump As Revealed by Experiments and Simulation

2006 ◽  
Vol 128 (5) ◽  
pp. 495-507 ◽  
Author(s):  
Ayako Takeuchi ◽  
Shuji Tatsumi ◽  
Nobuaki Sarai ◽  
Keisuke Terashima ◽  
Satoshi Matsuoka ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Cell Volume ◽  
Ventricular Myocytes ◽  
Cell Model ◽  
Drug Application ◽  
Membrane Depolarization ◽  
Cell Swelling ◽  
Cardiac Cell ◽  
Ionic Mechanisms ◽  
Ca2 Channels

Although the Na+/K+ pump is one of the key mechanisms responsible for maintaining cell volume, we have observed experimentally that cell volume remained almost constant during 90 min exposure of guinea pig ventricular myocytes to ouabain. Simulation of this finding using a comprehensive cardiac cell model (Kyoto model incorporating Cl− and water fluxes) predicted roles for the plasma membrane Ca2+-ATPase (PMCA) and Na+/Ca2+ exchanger, in addition to low membrane permeabilities for Na+ and Cl−, in maintaining cell volume. PMCA might help maintain the [Ca2+] gradient across the membrane though compromised, and thereby promote reverse Na+/Ca2+ exchange stimulated by the increased [Na+]i as well as the membrane depolarization. Na+ extrusion via Na+/Ca2+ exchange delayed cell swelling during Na+/K+ pump block. Supporting these model predictions, we observed ventricular cell swelling after blocking Na+/Ca2+ exchange with KB-R7943 or SEA0400 in the presence of ouabain. When Cl− conductance via the cystic fibrosis transmembrane conductance regulator (CFTR) was activated with isoproterenol during the ouabain treatment, cells showed an initial shrinkage to 94.2 ± 0.5%, followed by a marked swelling 52.0 ± 4.9 min after drug application. Concomitantly with the onset of swelling, a rapid jump of membrane potential was observed. These experimental observations could be reproduced well by the model simulations. Namely, the Cl− efflux via CFTR accompanied by a concomitant cation efflux caused the initial volume decrease. Then, the gradual membrane depolarization induced by the Na+/K+ pump block activated the window current of the L-type Ca2+ current, which increased [Ca2+]i. Finally, the activation of Ca2+-dependent cation conductance induced the jump of membrane potential, and the rapid accumulation of intracellular Na+ accompanied by the Cl− influx via CFTR, resulting in the cell swelling. The pivotal role of L-type Ca2+ channels predicted in the simulation was demonstrated in experiments, where blocking Ca2+ channels resulted in a much delayed cell swelling.

scholarly journals Sulfate Flux in High Sodium Cat Red Cells

1972 ◽  
Vol 59 (2) ◽  
pp. 155-166 ◽  
Author(s):  
R. I. Sha'afi ◽  
E. Pascoe
Keyword(s):  
Steady State ◽  
Cell Volume ◽  
Rate Constant ◽  
Incubation Medium ◽  
Red Cells ◽  
Bathing Medium ◽  
High Sodium ◽  
Sulfate Flux ◽  
Na Uptake

The transport of radioactive sulfate in cat red cells has been studied. The rate constant for 35SO4 inward movement under steady-state conditions is 0.24 ± 0.02/hr. This movement was found to be sensitive to osmotic changes in cell volume and to the nature of anions in the incubation medium; it increases with increasing cell volume and decreases with decreasing cell volume. The anions SCN, NO3, and I were found to inhibit the uptake of 35SO4. Furthermore, 1-fluoro-2,4-dinitrobenzene at a concentration of 1 mM inhibits (>90%) this uptake. The inward movement of erythritol-14C shows qualitatively the same dependence on cell volume as 35SO4, but it is insensitive to the nature of the anion present in the bathing medium. It was also found that the usually observed inhibition of radioactive Na uptake by SCN in cat red cells can be reversed when cell volume is increased.

Sign in / Sign up

Export Citation Format

Share Document