Tetraphenylphosphonium ion is a true indicator of negative plasma-membrane potential in the yeast Rhodotorula glutinis. Experiments under osmotic stress and at low external pH values

M Höfer; A Künemund

doi:10.1042/bj2250815

Tetraphenylphosphonium ion is a true indicator of negative plasma-membrane potential in the yeast Rhodotorula glutinis. Experiments under osmotic stress and at low external pH values

Biochemical Journal ◽

10.1042/bj2250815 ◽

1985 ◽

Vol 225 (3) ◽

pp. 815-819 ◽

Cited By ~ 15

Author(s):

M Höfer ◽

A Künemund

Keyword(s):

Plasma Membrane ◽

Membrane Potential ◽

Osmotic Stress ◽

Electrical Potential ◽

Rhodotorula Glutinis ◽

Resistant Mutant ◽

Electrical Potential Difference ◽

Ph Values ◽

Negative Membrane Potential ◽

In The Wild

In the yeast Rhodotorula glutinis, accumulation of the tetraphenylphosphonium ion (TPP+) was increased under conditions of osmotic stress, indicating a hyperpolarization of the negative membrane potential (delta psi). The following observations were consistent with the occurrence of hyperpolarized delta psi: enhanced accumulation of glucosamine, the uptake of which is also driven by delta psi; increased respiratory rate. The accumulation of TPP+ was gradually decreased by lowering the pH of cell suspensions. At pH values below 4.5, no TPP+ was taken up, but instead thiocyanate (SCN-) was accumulated, indicating a positive delta psi. The pH-dependent influx of glucosamine followed the pattern of TPP+ accumulation both in the wild-type and in the nystatin-resistant mutant, M67, which displayed a negative delta psi down to pH 3. Thus TPP+ accumulation in Rh. glutinis reflected actual electrical potential difference across the plasma membrane.

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Sex differences in membrane potential in the intact perfused rat liver

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1988.255.6.g822 ◽

1988 ◽

Vol 255 (6) ◽

pp. G822-G825 ◽

Cited By ~ 2

Author(s):

R. A. Weisiger ◽

J. G. Fitz

Keyword(s):

Sex Differences ◽

Plasma Membrane ◽

Membrane Potential ◽

Electrical Potential ◽

Hepatic Uptake ◽

Female Rats ◽

Electrical Potential Difference ◽

Bicarbonate Buffer ◽

Male And Female Rats ◽

Negative Membrane Potential

The electrical potential difference across the plasma membrane was compared in paired livers from male and female rats perfused single-pass with Krebs-bicarbonate buffer. Variability in the membrane potential measured for different cells within the same liver was small (SD = 1.3 mV). The mean membrane potential was 5.1 mV more negative for male livers than for female livers (-30.3 +/- 0.6 vs. -25.2 +/- 1.0 mV, P less than 0.001), and the male liver had a more negative membrane potential than the female liver in all nine pairs studied. No correlation between membrane potential and perfusion rate was seen. Variability among female livers was more than twice as great (range -19.6 to -30.0 mV) as for male livers (range -26.7 to -31.9 mV). These results suggest that hepatic membrane potential may be modulated by sex hormone levels, which are more variable in female animals. Because the hepatic uptake of bile acids such as taurocholate and organic anions such as bilirubin may involve net movement of electrical charge across the plasma membrane, the current results may explain previously reported sex differences in the uptake of these and other electrogenically transported molecules.

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Adiponectin hormone and Measurements of Plasma Membrane Voltage in Isolated Adipocytes of Control and Diabetic Patients.

International Journal of Medical Sciences ◽

10.32441/ijms.v1i3.100 ◽

2018 ◽

Vol 1 (3) ◽

pp. 39-42

Author(s):

Mohammed F Alkotobe ◽

Nabaa Saad Ibadi

Keyword(s):

Plasma Membrane ◽

Electrical Potential ◽

Cellular Level ◽

Economic Problem ◽

Membrane Voltage ◽

Diabetic Patients ◽

Electrical Potential Difference ◽

Significant Difference ◽

Isolated Adipocytes ◽

Inflammatory Changes

Background: Diabetes is one of the most important and social-economic problem worldwide and characterized by serious metabolic, vascular and neurologic complications. Aim: To isolate adipocytes in diabetic patients and estimate the electrical potential difference (membrane potential) of isolated adipocytes. Methods: Biopsy of lipid tissue of diabetic patients were taken In Bin-Sina hospital and then adipocytes were isolated in laboratory of College of Science, Baghdad University.. Results: The Adiponectin mean serum value was significantly (P<0.001) higher in diabetic patients (15.60 ± 1.73 g/ml) as compared to controls (5.80 ± 1.22 g/ml). While the measurement of isolated adipocytes current was significantly (P<0.001) different in diabetic patients (-30.4 ± 4 mV) from that in controls ( -61 ± 5mV). Conclusion: Adipocytes plasma membrane voltage was with significant difference in diabetic patients as compared to controls and this reflect the inflammatory changes at cellular level in diabetes.

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Generation of resting membrane potential

AJP Advances in Physiology Education ◽

10.1152/advan.00029.2004 ◽

2004 ◽

Vol 28 (4) ◽

pp. 139-142 ◽

Cited By ~ 79

Author(s):

Stephen H. Wright

Keyword(s):

Membrane Potential ◽

Animal Cell ◽

Electrical Potential ◽

Quantitative Relationship ◽

Resting Membrane Potential ◽

First Year ◽

General View ◽

Electrical Potential Difference ◽

Physiological Basis ◽

Students First

This brief review is intended to serve as a refresher on the ideas associated with teaching students the physiological basis of the resting membrane potential. The presentation is targeted toward first-year medical students, first-year graduate students, or senior undergraduates. The emphasis is on general concepts associated with generation of the electrical potential difference that exists across the plasma membrane of every animal cell. The intention is to provide students a general view of the quantitative relationship that exists between 1) transmembrane gradients for K+ and Na+ and 2) the relative channel-mediated permeability of the membrane to these ions.

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Use of Membrane Potential Measurements to Study Mode of Action of Diclofop-Methyl

Weed Science ◽

10.1017/s0043174500080401 ◽

1994 ◽

Vol 42 (2) ◽

pp. 285-292 ◽

Cited By ~ 10

Author(s):

John P. Wright

Keyword(s):

Membrane Potential ◽

Energy Metabolism ◽

Electrical Potential ◽

Potential Gradient ◽

Membrane Vesicles ◽

Proton Pumping ◽

Transport Processes ◽

Membrane Properties ◽

Electrical Potential Difference ◽

Study Mode

All actively metabolizing cells have an electrical potential difference, negative on the interior, across their membranes. This electrochemical potential gradient is generated primarily by proton-pumping ATPases and provides the driving force for the transport of various ionic and neutral solutes. It is a key element in the energy metabolism of cells. Such factors as alteration of transport processes, energy metabolism, cytoplasmic pH, and membrane permeability have a direct effect on the magnitude of the membrane potential. In a brief survey, diclofop-methyl, diclofop, hydroxydiclofop, CGA 82725, haloxyfop-methyl, haloxyfop, bentazon, dinoseb, 4-hydroxy CIPC, and 2-hydroxy CIPC caused rapid depolarizations of the membrane potential of oat coleoptiles. Chlorsulfuron, dimethipin, propham, CIPC, dicamba, alachlor, metolachlor, napthalic anhydride, and paraquat had no measurable effects. The depolarizing effects of diclofop-reported earlier are used to illustrate the methods and interpretation of plant cell membrane potential measurements. Diclofop and diclofop-methyl affect the membrane properties of sensitive plant cells. Diclofop irreversibly depolarized the membrane potential and increased the proton permeability of sensitive cells but not resistant cells. It also increased the ATPase activity of isolated membrane vesicles. The mechanism through which diclofop exerted its effect is not fully understood. The equipment and techniques required for the intercellular recording of membrane potentials and resistance are described as well as the limitations of the techniques. A method not used in herbicide studies but with great potential for studies of herbicide interactions with membranes is patch clamp. A brief introduction to the methods will be given.

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Intracellular pH and membrane potassium conductance in rabbit distal colon

AJP Cell Physiology ◽

10.1152/ajpcell.1990.258.2.c336 ◽

1990 ◽

Vol 258 (2) ◽

pp. C336-C343 ◽

Cited By ~ 13

Author(s):

M. E. Duffey ◽

D. C. Devor

Keyword(s):

Membrane Potential ◽

Intracellular Ph ◽

Basolateral Membrane ◽

Electrical Potential ◽

Potassium Conductance ◽

Co2 Concentration ◽

Distal Colon ◽

Bathing Solution ◽

Electrical Potential Difference ◽

K Concentration

Intracellular pH (pHc) was measured in the short-circuited epithelium of rabbit distal colon using H(+)-selective microelectrodes. pHc was 6.91 +/- 0.02 (SE) when the bath pH was 7.4. Intracellular HCO3- activity (acHCO3-) was estimated from these measurements to be 8 +/- 0 mM. When we replaced all Cl- in the tissue bathing solutions with the impermeant anion gluconate, pHc rose to 7.44 +/- 0.08 and acHCO3- increased to 30 +/- 6 mM. These results demonstrate that this tissue contains a Cl(-)-HCO3- exchange mechanism. During the Cl- replacement the apical membrane electrical potential difference hyperpolarized from -55 +/- 1 to -74 +/- 3 mV, suggesting that membrane ionic conductance had changed. Elevation of either the apical or basolateral membrane bathing solution K+ concentration produced a greater depolarization of membrane potential during Cl- replacement than when tissues were bathed in normal electrolyte solutions. In additional experiments, pHc was raised by lowering the bath CO2 concentration while the bath Cl- concentration was kept normal. Under these conditions, membrane potential hyperpolarized and was more sensitive to the elevation of bath K+ concentration than when pHc was normal. These results suggest that membrane K+ conductance in this tissue is increased by intracellular alkalinization.

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Hepatic uptake of 3,5,3'-triiodothyronine: electrochemical driving forces

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1992.262.6.g1104 ◽

1992 ◽

Vol 262 (6) ◽

pp. G1104-G1112

Author(s):

R. A. Weisiger ◽

B. A. Luxon ◽

R. R. Cavalieri

Keyword(s):

Plasma Membrane ◽

Active Transport ◽

Driving Forces ◽

Electrical Potential ◽

Hepatic Uptake ◽

Electrical Potential Difference ◽

Multiple Indicator Dilution ◽

Multiple Indicator ◽

Basolateral Plasma Membrane ◽

Uptake Process

We used the multiple indicator dilution technique to assess the electrochemical forces driving uptake of 3,5,3'-triiodo-L-thyronine (T3) across the basolateral plasma membrane in the single-pass perfused rat liver. With the use of 4 g/dl albumin solutions, the influx and efflux clearances were 0.020 +/- 0.005 and 0.0049 +/- 0.0017 (SE) ml.s-1.g liver-1, respectively, indicating that the total T3 concentration at equilibrium should be about four times greater in cytoplasm than in plasma. However, when the influx and efflux clearances were divided by the unbound (free) T3 concentration in the perfusate and cytosol, they were not different (3.76 +/- 0.26 vs. 4.30 +/- 0.38 ml.s-1.g liver-1), indicating that the uptake process does not generate a gradient of unbound T3 across the plasma membrane. To further test whether T3 uptake is driven by the electrical potential difference across the plasma membrane, liver cells were depolarized by isosmotic replacement of perfusate chloride with gluconate. There was no effect on uptake or efflux. To test whether uptake is coupled to influx of sodium, perfusate sodium was replaced with choline. Although there was a modest decline in both the influx and efflux clearances, there was no change in their ratio, as would be expected for sodium-coupled active transport. These results indicate that uptake of T3 across the basolateral hepatocyte membrane occurs by passive diffusion. We found no evidence to support concentrative, active transport by either electrogenic or sodium-coupled mechanisms.

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Hepatic taurine transport: a Na+-dependent carrier on the basolateral plasma membrane

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1987.253.3.g351 ◽

1987 ◽

Vol 253 (3) ◽

pp. G351-G358 ◽

Cited By ~ 3

Author(s):

J. C. Bucuvalas ◽

A. L. Goodrich ◽

F. J. Suchy

Keyword(s):

Plasma Membrane ◽

Electrical Potential ◽

Maximum Velocity ◽

Membrane Vesicles ◽

Hepatic Uptake ◽

Electrical Potential Difference ◽

Plasma Membrane Vesicles ◽

Liver Plasma Membrane ◽

Na Ions ◽

Taurine Uptake

Highly purified rat basolateral liver plasma membrane vesicles were used to examine the mechanism and the driving forces for hepatic uptake of the beta-amino acid, taurine. An inwardly directed 100 mM NaCl gradient stimulated the initial rate of taurine uptake and energized a transient twofold accumulation of taurine above equilibrium ("overshoot"). In contrast, uptake was slower and no overshoot was detected in the presence of a KCl gradient. A negative intravesicular electrical potential generated by the presence of permeant anions or an outwardly directed K+ gradient with valinomycin increased Na+-stimulated taurine uptake. External Cl- stimulated Na+-dependent taurine uptake independent of effects on the transmembrane electrical potential difference. Na+-dependent taurine uptake showed a sigmoidal dependence on extravesicular Na+ concentration, suggesting multiple Na+ ions are involved in the translocation of each taurine molecule. Na+-dependent taurine uptake demonstrated Michaelis-Menten kinetics with a maximum velocity of 0.537 nmol.mg protein-1.min-1 and an apparent Km of 174 microM. [3H]taurine uptake was inhibited by the presence of excess unlabeled taurine, beta-alanine, or hypotaurine but not by L-glutamine or L-alanine. In summary, using basolateral liver plasma membrane vesicles, we have shown that hepatic uptake of taurine occurs by a carrier-mediated, secondary active transport process specific for beta-amino acids. Uptake is electrogenic, stimulated by external Cl-, and requires multiple Na+ ions for the translocation of each taurine molecule.

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Insulin action on membrane potential and glucose uptake: effects of high potassium

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1985.249.1.e17 ◽

1985 ◽

Vol 249 (1) ◽

pp. E17-E25

Author(s):

K. Zierler ◽

E. M. Rogus ◽

R. W. Scherer ◽

F. S. Wu

Keyword(s):

Membrane Potential ◽

Insulin Action ◽

Potassium Concentration ◽

Electrical Potential ◽

Cell Swelling ◽

Electrical Potential Difference ◽

High Potassium ◽

High K ◽

External Potassium ◽

Stimulation Of

These experiments were designed to test the hypothesis that insulin-induced hyperpolarization is a link in the chain of events leading to stimulation of glucose transport. External potassium concentration, [K+]o, was increased by equimolar substitution of KCl for NaCl, a method known to cause cell swelling, and by substitution of [K+]o for [Na+]o with maintenance of constant [K+]o X [Cl-]o product, a method that does not cause cell swelling. When there was constant KCl product, even at 76.8 meq [K+]o insulin continued to hyperpolarize, although by only approximately 44% as much as in normal [K+]o, and insulin-stimulated 2-deoxyglucose uptake was only approximately 60% of that at normal [K+]o. With equimolar substitution of KCl for NaCl: electrical potential difference across cell membranes of surface fibers of rat caudofemoralis muscle decreased with logarithm [K+]o, in the presence or absence of insulin. Insulin-induced hyperpolarization decreased as [K+]o increased and disappeared at 36 mM [K+]o. The amount of insulin bound to its receptors in 1 h was not affected by [K+]o over the range studied. Insulin effects on membrane potential and on 2-deoxyglucose uptake, as both were altered by [K+]o, correlated well. As the probe moved in depth through the first six fibers there was stepwise decrease in depolarization in high [K+]o in the absence of insulin. Insulin hyperpolarized the deepest of these fibers, even when it did not hyperpolarize the outermost. The decrease in insulin-induced hyperpolarization as [K+]o increases is consistent with the hypothesis that insulin hyperpolarizes by decreasing the ratio PNa/PK.

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