Sodium‐bicarbonate cotransport current in identified leech glial cells.

Munsch, Thomas; Deitmer, Joachim W.

doi:10.1113/jphysiol.1994.sp020001

Cited by 54 publications

(43 citation statements)

References 30 publications

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“…To increase the opening of the electrode-tip, it was bevelled with a jet stream of aluminum powder suspended in H 2 O. Calibration of the electrodes was carried out in oocyte salines with a pH of 7.0 and 6.4. The recording arrangement was the same as described previously (10,11). The central and reference barrels of the electrodes were connected by chloride-treated silver wires to the head-stages of an electrometer amplifier.…”

Section: Methodsmentioning

confidence: 99%

Voltage Dependence of H+ Buffering Mediated by Sodium Bicarbonate Cotransport Expressed in Xenopus Oocytes

Becker

Deitmer

2004

Journal of Biological Chemistry

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The electrogenic sodium bicarbonate cotransporter (NBCe1) is expressed in many epithelial cells and, in the brain, in glial cells. Little is known about the physiological significance of the NBCe1 for proton homeostasis and for other acid/base-coupled transporters in these cells. We have measured the voltage-dependent transport activity of an NBC from human kidney, type hkNBCe1, expressed in oocytes of the frog Xenopus laevis, by recording membrane current and the changes in intracellular pH and sodium at different membrane potentials between ؊20 and ؊100 mV. The apparent intracellular buffer capacity was increased and became dependent upon membrane voltage when the NBCe1 was expressed; the measured buffer capacity increased by up to 7 mM/10 mV of membrane depolarization. Lactate transport by the electroneutral monocarboxylate transporter became enhanced and dependent upon membrane potential, when the monocarboxylate transporter (isoform 1) was co-expressed with NBCe1 in oocytes. Our results indicate that the electrogenic NBCe1 renders the cell membrane potential an effective regulator of intracellular H ؉ buffering and acid/base-coupled metabolite transport.

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Section: Methodsmentioning

confidence: 99%

Voltage Dependence of H+ Buffering Mediated by Sodium Bicarbonate Cotransport Expressed in Xenopus Oocytes

Becker

Deitmer

2004

Journal of Biological Chemistry

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“…Changes in pH, of less than 0.5 pH unit in the range of 7.2 are large enough to influence the direction of bicarbonate transport. Because of its sensitivity to changes in pH, the Na+-HCO3-symporter may be involved in the regulation of extracellular pH (Munsch and Deitmer, 1994).A prerequisite for evaluating the potential affects of pH and Suc concentration changes on the rate of Suc transport is a knowledge of their concentration in vivo and knowledge of the kinetics parameters associated with transport. Determination of the kinetics parameters for Suc transport is the subject of this report.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Kinetics Analysis of the Plasma Membrane Sucrose-H+ Symporter from Sugar Beet (Beta vulgaris L.) Leaves

Buckhout¹

1994

Plant Physiol.

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The kinetics behavior of the H+-sucrose (Suc) symporter was investigated in plasma membrane vesicles from sugar beet (Beta vulgaris 1.) leaves by analyzing the effect of externa1 and internal pH (pH. and pHi, respectively) on Suc uptake. l h e apparent K,,, for Suc uptake increased 18-fold as the pH. increased from 5.5 to 7.5. Over this same pH, range, the apparent VmaX for Suc uptake remained constant. l h e effects of pHi in the presence or absence of internal Suc were exclusively restrided to changes in Vmx. Thus, proton concentration on the inside of the membrane vesicles ([H+]i) behaved as a noncompetitive inhibitor of Suc uptake. l h e K,,, for the proton concentration on the outside of the membrane vesicles was estimated to be pH 6.3, which would indicate that at physiological apoplastic pH Suc transport might be sensitive to changes in pH,. On the other hand, the Suc transport across the PM is catalyzed by an H+-Suc symporter (Buckhout, 1989;Bush, 1989; Lemoine and Delrot, 1989; Williams et al., 1990). Transport is driven by the proton motive force established across the PM by the H+-ATPase in vivo and is electrogenic (Bush, 1990; Slone and Buckhout, 1991). The movement of H+ and Suc is tightly coupled with a stoichiometry of 1:l (Slone and Buckhout, 1991), and the carrier is specific for the Suc molecule, although phenylglucosides are also recognized by the carrier (Hecht et al., 1992). Finally, a gene encoding the H+-Suc symport protein was recently identified in spinach leaf cells (Riesmeier et al., 1992). In the plant, this transporter is responsible for phloem loading and, thus, photoassimilate export from leaves in many plant species (Giaquinta, 1983;Bush, 1993;Riesmeier et al., 1993).The membrane vesicle system offers the advantage for the kinetics analysis of transport processes that the driver ion and solute concentration on both sides of the vesicle mem- brane can be varied, and it has the further advantage that effects of tissue thickness and substrate access are eliminated (Ehwald et al., 1979). Determination of the kinetics parameters of a transport process can provide predictive insight into the behavior of the transporter in vivo. For example, if the apparent K, for [H' ], of the H+-Suc symporter is approximately equal to pH,, then changes in pH, could significantly affect the rate of Suc uptake. The same would hold true for for inhibition of uptake by [H+]i. Thus, a decrease in pH, might significantly inhibit Suc uptake, as is the case for H+-dependent C1-uptake in Chara (Sanders and Hansen, 1981).On the other hand, a single carrier might be involved in influx and efflux depending on the local concentrations of the ligands and the relative sensitivity of the carrier to changes in ligand concentration. Such macroscopic reversibility is found, for example, in the Na+-HC03-symporter in glial cells. This symporter catalyzes the movement of Na+ and HC03-with inward transport being stimulated by increasing concentration of HC03-outside of the membrane vesicles or by membrane depolarization, ...

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“…The other signalling pathway activated by uncaging GTP-␥-S in the giant glial cell resulted in the release of Ca 2+ from intracellular stores mediated by phospholipase C (PLC) and the production of IP 3 (Berridge et al, 2003 (Annunziato et al, 2004;DiPolo and Beaugé, 2006). In the leech giant glial cell, we could show that both plasmalemmal Ca 2+ -ATPase and Na + /Ca 2+ exchange contribute to the recovery of Ca 2+ from a cytosolic rise (Nett and Deitmer, 1998a). In rat cerebellar astrocytes, Na + /Ca 2+ exchange was shown to be responsible for maintaining a low resting cytosolic Ca 2+ (DiPolo and Beaugé, 2006).…”

Section: Activation Of G Proteins By Uncaging Of Gtp-␥-smentioning

confidence: 63%

“…The increase in K + conductance induced by the uncaging of GTP-␥-S was not due to the hyperpolarization per se, since the glial cell current-voltage relationship is nearly linear over the potential range of -50 to -100·mV (not shown here) (Munsch and Deitmer, 1994). The glial responses to myomodulin and Leydig neuron stimulation and to 5-HT could be blocked by the injection of the non-hydrolyzable G protein inhibitor GDP-␤-S (Britz et al, 2004;Britz et al, 2005).…”

Section: Injection Of Gdp-␤-s or Gdpmentioning

confidence: 87%

G protein activation by uncaging of GTP-γ-S in the leech giant glial cell

Hirth

Britz

Deitmer

2007

Journal of Experimental Biology

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SUMMARY Glial cells can be activated by neurotransmitters viametabotropic, G protein-coupled receptors. We have studied the effects of`global' G protein activation by GTP-γ-S on the membrane potential,membrane conductance, intracellular Ca2+ and Na+ of the giant glial cell in isolated ganglia of the leech Hirudo medicinalis. Uncaging GTP-γ-S (injected into a giant glial cell as caged compound) by moderate UV illumination hyperpolarized the membrane due to an increase in K+ conductance. Uncaging GTP-γ-S also evoked rises in cytosolic Ca2+ and Na+, both of which were suppressed after depleting the intracellular Ca2+ stores with cyclopiazonic acid (20 μmol l–1). Uncaging inositol-trisphosphate evoked a transient rise in cytosolic Ca2+ and Na+ but no change in membrane potential. Injection of the fast Ca2+ chelator BAPTA or depletion of intracellular Ca2+ stores did not suppress the membrane hyperpolarization induced by uncaging GTP-γ-S. Our results suggest that global activation of G proteins in the leech giant glial cell results in a rise of Ca2+-independent membrane K+conductance, a rise of cytosolic Ca2+, due to release from intracellular stores, and a rise of cytosolic Na+, presumably due to increased Na+/Ca2+ exchange.

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Sodium‐bicarbonate cotransport current in identified leech glial cells.

Cited by 54 publications

References 30 publications

Voltage Dependence of H+ Buffering Mediated by Sodium Bicarbonate Cotransport Expressed in Xenopus Oocytes

Voltage Dependence of H+ Buffering Mediated by Sodium Bicarbonate Cotransport Expressed in Xenopus Oocytes

Kinetics Analysis of the Plasma Membrane Sucrose-H+ Symporter from Sugar Beet (Beta vulgaris L.) Leaves

G protein activation by uncaging of GTP-γ-S in the leech giant glial cell

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