Interactions of cell volume, membrane potential, and membrane transport parameters

1980 ◽  
Vol 238 (5) ◽  
pp. C196-C206 ◽  
Author(s):  
E. Jakobsson
Keyword(s):  
Membrane Potential ◽  
Cell Volume ◽  
Membrane Transport ◽  
Numerical Solutions ◽  
Transport Equations ◽  
Time Varying ◽  
Transport Parameters ◽  
Animal Cells ◽  
Analytic Expressions ◽  
Solute Species

Equations have been written and solved that describe for animal cells the relationships among membrane transport, cell volume, membrane potential, and distribution of permeant solute. The essential system consists of n + 2 equations, where n is the number of permeant solute species. The n of the equations are the n transport equations for the permeant species, one for each species. The other two equations are statements of 1) the condition for bulk electroneutrality inside the cell and 2) the condition for isotonicity between the interior and exterior of the cell. Numerical solutions have been obtained in both the steady-state and time-varying cases for transport equations that are physically and phenomenologically reasonable. In addition to numerical solutions analytic expressions are presented that show the ranges of membrane parameters essential for volume regulation; for values of membrane parameters beyond explicitly defined bounds, the equations do not have real, positive solutions for cell volume.

An Extended Analytic Expression for the Membrane Potential Distribution of Conductance-Based Synaptic Noise

2005 ◽  
Vol 17 (11) ◽  
pp. 2301-2315 ◽  
Author(s):  
M. Rudolph ◽  
A. Destexhe
Keyword(s):  
Membrane Potential ◽  
Stochastic Processes ◽  
Potential Distribution ◽  
Numerical Solutions ◽  
Stochastic Calculus ◽  
Expectation Values ◽  
Synaptic Currents ◽  
Synaptic Noise ◽  
Analytic Expressions

Synaptically generated subthreshold membrane potential (Vm) fluctuations can be characterized within the framework of stochastic calculus. It is possible to obtain analytic expressions for the steady-state Vm distribution, even in the case of conductance-based synaptic currents. However, as we show here, the analytic expressions obtained may substantially deviate from numerical solutions if the stochastic membrane equations are solved exclusively based on expectation values of differentials of the stochastic variables, hence neglecting the spectral properties of the underlying stochastic processes. We suggest a simple solution that corrects these deviations, leading to extended analytic expressions of the Vm distribution valid for a parameter regime that covers several orders of magnitude around physiologically realistic values. These extended expressions should enable finer characterization of the stochasticity of synaptic currents by analyzing experimentally recorded Vm distributions and may be applicable to other classes of stochastic processes as well.

scholarly journals Role of glutathione on cell adhesion and volume.

2021 ◽  
Author(s):  
Alain Geloen ◽  
Emmanuelle Danty
Keyword(s):  
Cell Adhesion ◽  
Cell Volume ◽  
Reduced Glutathione ◽  
Self Regulation ◽  
Cell Types ◽  
Self Control ◽  
Animal Cells ◽  
Cellular Processes ◽  
Proliferation And Apoptosis ◽  
Glutamylcysteine Synthetase

Glutathione is the most abundant thiol in animal cells. Reduced glutathione (GSH) is a major intracellular antioxidant neutralizing free radicals and detoxifying electrophiles. It plays important roles in many cellular processes, including cell differentiation, proliferation, and apoptosis. In the present study we demonstrate that extracellular concentration of reduced glutathione markedly increases cell volume within few hours, in a dose-response manner. Pre-incubation of cells with BSO, the inhibitor of 7-glutamylcysteine synthetase, responsible for the first step in intracellular glutathione synthesis did not change the effect of reduced glutathione on cell volume suggesting a mechanism limited to the interaction of extracellular reduced glutathione on cell membrane. Results show that reduced GSH decreases cell adhesion resulting in an increased cell volume. Since many cell types are able to transport of GSH out, the present results suggest that this could be a fundamental self-regulation of cell volume, giving the cells a self-control on their adhesion proteins.

Effect of isosmotic removal of extracellular Ca2+ and of membrane potential on cell volume in muscle cells

1994 ◽  
Vol 267 (3) ◽  
pp. C768-C775 ◽  
Author(s):  
C. Pena-Rasgado ◽  
K. D. McGruder ◽  
J. C. Summers ◽  
H. Rasgado-Flores
Keyword(s):  
Membrane Potential ◽  
Sarcoplasmic Reticulum ◽  
Cell Volume ◽  
Muscle Cells ◽  
Membrane Depolarization ◽  
Volume Reduction ◽  
Sensitive Volume ◽  
Volume Increase ◽  
Dependent Cell ◽  
In Cells

Isosmotic removal of extracellular Ca2+ (Cao) and changes in membrane potential (Vm) are frequently performed manipulations. Using isolated voltage-clamped barnacle muscle cells, we studied the effect of these manipulations on isosmotic cell volume. Replacing Cao by Mg2+ induced 1) verapamil-sensitive extracellular Na(+)-dependent membrane depolarization, 2) membrane depolarization-dependent cell volume reduction in cells whose sarcoplasmic reticulum (SR) was presumably loaded with Ca2+ [intracellular Ca2+ (Cai)-loaded cells], and 3) cell volume increase in cells whose SR was presumably depleted of Ca2+ (Cai-depleted cells) or in Cai-loaded cells whose Vm was held constant. Membrane depolarization induced 1) volume reduction in Cai-loaded cells or 2) verapamil-sensitive volume increase in Cai-depleted cells. This suggests tha, in Cai-loaded cells, membrane depolarization induces SR Ca2+ release, which in turn promotes volume reduction. Conversely, in Cai-depleted cells, the depolarization activates Na+ influx through a verapamil-sensitive pathway leading to the volume increase. This pathway is also revealed when Cao is removed in either Cai-depleted cells or in cells whose Vm is held constant.

An NMR study of cellular phosphates and membrane transport in renal proximal tubules

1995 ◽  
Vol 268 (3) ◽  
pp. F375-F384 ◽  
Author(s):  
M. C. Chobanian ◽  
M. E. Anderson ◽  
P. C. Brazy
Keyword(s):  
Membrane Potential ◽  
Membrane Transport ◽  
Basolateral Membrane ◽  
Barium Chloride ◽  
Partial Replacement ◽  
Transport Mechanisms ◽  
Extracellular Medium ◽  
Protein Inhibition ◽  
Nmr Study ◽  
Perifusion System

Technical limitations in the measurement of cellular phosphates have hindered studies of interrelationships between cellular Pi, its transport, and its metabolism in renal proximal tubule (PT) cells. We have developed a noninvasive 31P-nuclear magnetic resonance (NMR) probe-perifusion system to measure cellular Pi and have utilized this system to investigate relationships in canine PT cells between the membrane transport and the cellular content of Pi. With 1.2 mM Pi in the extracellular medium, the cellular Pi content of PT averaged 4.94 +/- 0.55 nmol/mg protein. Inhibition of Pi uptake by removal of extracellular Pi rapidly decreased all cellular phosphate compounds to values that were between 55 and 85% of control. Partial replacement of extracellular Pi (0.4 mM) increased cellular phosphates up to 84-100% of control values. Inhibition of Na(+)-K(+)-adenosinetriphosphatase uptake by the addition of ouabain failed to change either cellular Pi or organic phosphates. Reducing the basolateral membrane potential with the addition of barium chloride increased cellular Pi content by nearly 30%. Maximal contents of cellular Pi and ATP were achieved at 0.4 mM Pi in the presence of an inwardly directed Na+ gradient and at 0.8 mM Pi in its absence. These data indicate that cellular Pi content in canine PT is regulated by Na(+)-dependent and -independent transport mechanisms and by the membrane potential across the basolateral membrane. Lastly, cellular ATP content was found to be directly proportional to the cellular Pi content over a physiological range.

Comparative Freezing Response of Ejaculated and Epididymal Rhesus Monkey Sperm

2008 ◽  
Author(s):  
Raghava Alapati ◽  
Kelly Goff ◽  
Hans-Michael Kubisch ◽  
Ram V. Devireddy
Keyword(s):  
Rhesus Monkey ◽  
Membrane Permeability ◽  
Cell Volume ◽  
Water Transport ◽  
Sperm Cell ◽  
Transport Parameters ◽  
Cryoprotective Agents ◽  
Transport Response ◽  
Bovine Spermatozoa ◽  
Inactive Cell

In the present study, we report the effects of cooling ejaculated and epididymal rhesus monkey (Macaca mulatta) sperm in the presence of extracellular. Water transport data during freezing of ejaculated and epididymal sperm cell suspensions were obtained at a cooling rate of 20 °C/min in the absence of any cryoprotective agents. Additional water transport data was obtained from ejaculated sperm at a cooling of 5 °C/min without CPAs and at 20 °C/min in the presence of 0.7M of glycerol, as well. Using previously published values, the bovine sperm cell was modeled as a cylinder of length 73.83 μm and a radius of 0.32 μm with an osmotically inactive cell volume, Vb, of 0.772Vo, where Vo is the isotonic cell volume. The subzero water transport response is analyzed to determine the variables governing the rate of water loss during cooling of bovine spermatozoa, i.e. the membrane permeability parameters (reference membrane permeability, Lpg and activation energy, ELp). The predicted best-fit permeability parameters ranged from, Lpg = 0.0023 to 0.0029 μm/min-atm and ELp = 10.6 to 45.5 kcal/mol. The subzero water transport response and consequently the subzero water transport parameters are not significantly different between the ejaculated and epididymal macaque spermatozoa under corresponding cooling conditions.

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.

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