Effects of Cation Binding to the Intracellular Vestibule of TMEM16 Ion Transport Pathways

Radioisotopic flux measurements were performed on rabbit Clara cell epithelium cultured in serum-free hormone-supplemented medium to identify the major ion transport pathways in the cell type. Clara cells cultured in serum-free hormone-supplemented medium exhibit a large short-circuit current compared with cells maintained in serum-containing medium (45 microA/cm2 vs. 15 microA/cm2). The responses to amiloride and isoproterenol, however, are similar for cells grown in the two media. A net amiloride-sensitive movement of Na+ in the mucosal (M)-to-serosal (S) direction undershort- and open-circuit conditions is detected (1.48 and 0.67 mueq.h-1.cm-2, respectively). No statistically significant difference in the unidirectional fluxes of Cl- is apparent in the basal state, but a net flux of Cl- in the S-to-M direction is observed after exposure of the apical membrane to amiloride (0.93 mueq.h-1.cm-2). The partial ionic conductances for Na+ and Cl- estimated from the fluxes measured in the passive directions (JNaS----M, JClM----S) exceed the total tissue conductance by 20%. Ussing flux ratio analyses of Cl- movements at clamped potentials between -60 and +20 mV show that Cl- movements are not strictly through passive conductive pathways at negative potentials. The movement of Cl- can be modeled by passive diffusion combined with Cl- -Cl- exchange equal to 20% of total passive fluxes of Na+ and Cl-. These observations indicate that 1) Na+ absorption is the major active ion transport pathway across cultured Clara cells, 2) active Cl- secretion is minimal in the basal state, and 3) approximately 20% of the unidirectional Cl- fluxes occur via nonconductive pathways.

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Active ion transport pathways in the bovine retinal pigment epithelium.

The Journal of Physiology ◽

10.1113/jphysiol.1990.sp018067 ◽

1990 ◽

Vol 424 (1) ◽

pp. 283-300 ◽

Cited By ~ 80

Author(s):

S S Miller ◽

J L Edelman

Keyword(s):

Retinal Pigment Epithelium ◽

Ion Transport ◽

Pigment Epithelium ◽

Retinal Pigment ◽

Transport Pathways ◽

Active Ion Transport

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Effects of a short-chain phospholipid on ion transport pathways in rabbit nasal airway epithelium

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1996.271.4.l646 ◽

1996 ◽

Vol 271 (4) ◽

pp. L646-L655 ◽

Cited By ~ 1

Author(s):

M. Ropke ◽

M. Hansen ◽

S. Carstens ◽

P. Christensen ◽

G. Danielsen ◽

...

Keyword(s):

Ion Transport ◽

Airway Epithelium ◽

Short Circuit ◽

Apical Cell ◽

Short Chain ◽

Nasal Airway ◽

Na Channels ◽

Transport Pathways ◽

Lipoxygenase Inhibitors ◽

Ussing Chambers

We investigated the mechanism of interference of mucosal application of the short-chain phospholipid didecanoyl-L-alpha-phosphatidylcholine (DDPC; 0.1-0.5%) with ion transport pathways in isolated rabbit nasal airway epithelium (RNAE). Transports of Na+ and Cl- were evaluated from tracer ion fluxes, short-circuit current (Isc), and epithelial conductance (Gt) under short-circuit conditions in Ussing chambers. DDPC rapidly and reversibly abolished net Na+ absorption, reduced control Isc (approximately 110 microA/cm2) by approximately 80%, and induced a small Cl secretion. Intracellular Ca2+ concentration ([Ca2+]i) increased dose dependently and transiently (measured by fura 2 in cultured rabbit airway epithelium), but ionomycin failed to mimic the decrease in Isc. The rise in [Ca2+]i may explain a Ba(2+)-sensitive transient activation of a basolateral K+ conductance. Indomethacin-sensitive prostaglandin E2 production in RNAE increased severalfold, but cyclooxygenase and lipoxygenase inhibitors did not prevent DDPC-induced changes in Isc. DDPC initially decreased control Gt (approximately 13 mS/cm2) by approximately 25% due to inhibition of amiloride-sensitive Na+ channels, and then reversibly increased Gt to approximately 45% above control values. Passive Na+ fluxes increased more than Cl fluxes, suggesting that the increase in Gt is due to formation of a paracellular shunt conductance in parallel with unaffected, anion-selective tight junction channels. The results suggest that DDPC inhibits apical membrane Na+ channels and causes structural changes in tight junctions after incorporation in apical cell membranes.

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A safe and fast-charging lithium-ion battery anode using MXene supported Li3VO4

Journal of Materials Chemistry A ◽

10.1039/c9ta02037c ◽

2019 ◽

Vol 7 (18) ◽

pp. 11250-11256 ◽

Cited By ~ 24

Author(s):

Yanghang Huang ◽

Haochen Yang ◽

Yi Zhang ◽

Yamin Zhang ◽

Yutong Wu ◽

...

Keyword(s):

Ion Transport ◽

Lithium Ion Battery ◽

Anode Material ◽

Three Dimensional ◽

Lithium Ion ◽

Ionic Transport ◽

Transport Pathways ◽

Fast Charging ◽

Battery Anode

An innovative anode material of lithium-ion battery, Li3VO4/Ti3C2Tx, was synthesized. The overall three-dimensional electronic and ionic transport pathways were formed in anode, which promoted both electron and ion transport during the lithiation and delithiation processes.

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Measuring ion transport activities in Xenopus oocytes using the ion-trap technique

AJP Cell Physiology ◽

10.1152/ajpcell.00560.2007 ◽

2008 ◽

Vol 295 (5) ◽

pp. C1464-C1472 ◽

Cited By ~ 6

Author(s):

Maxime G. Blanchard ◽

Jean-Philippe Longpré ◽

Bernadette Wallendorff ◽

Jean-Yves Lapointe

Keyword(s):

Steady State ◽

Ion Transport ◽

Ion Trap ◽

Large Diameter ◽

Cation Binding ◽

Monocarboxylate Transporter ◽

Charge Movement ◽

Xenopus Laevis Oocyte ◽

Selective Electrode ◽

Membrane Hyperpolarization

The ion-trap technique is an experimental approach allowing measurement of changes in ionic concentrations within a restricted space (the trap) comprised of a large-diameter ion-selective electrode apposed to a voltage-clamped Xenopus laevis oocyte. The technique is demonstrated with oocytes expressing the Na+/glucose cotransporter (SGLT1) using Na+- and H+-selective electrodes and with the electroneutral H+/monocarboxylate transporter (MCT1). In SGLT1-expressing oocytes, bath substrate diffused into the trap within 20 s, stimulating Na+/glucose influx, which generated a measurable decrease in the trap Na+ concentration ([Na+]T) by 0.080 ± 0.009 mM. Membrane hyperpolarization produced a further decrease in [Na+]T, which was proportional to the increased cotransport current. In a Na+-free, weakly buffered solution (pH 5.5), H+ drives glucose transport through SGLT1, and this was monitored with a H+-selective electrode. Proton movements can also be clearly detected on adding lactate to an oocyte expressing MCT1 (pH 6.5). For SGLT1, time-dependent changes in [Na+]T or [H+]T were also detected during a membrane potential pulse (150 ms) in the presence of substrate. In the absence of substrate, hyperpolarization triggered rapid reorientation of SGLT1 cation binding sites, accompanied by cation capture from the trap. The resulting change in [Na+]T or [H+]T is proportional to the pre-steady-state charge movement. The ion-trap technique can thus be used to measure steady-state and pre-steady-state transport activities and provides new opportunities for studying electrogenic and electroneutral ion transport mechanisms.

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Methylprednisolone increases absorptive capacity of rabbit ileum in vitro

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1983.245.4.g562 ◽

1983 ◽

Vol 245 (4) ◽

pp. G562-G567 ◽

Cited By ~ 1

Author(s):

J. H. Sellin ◽

R. C. DeSoignie

Keyword(s):

Ion Transport ◽

Absorptive Capacity ◽

Short Circuit ◽

Short Circuit Current ◽

Ion Flux ◽

Rabbit Ileum ◽

Transport Pathways ◽

Na Pump ◽

Intestinal Ion Transport

The effect of glucocorticoids on intestinal ion transport was studied in ileum in vitro from control and methylprednisolone (MP)-treated (40 mg im for 2 days) rabbits under the following conditions: a) basal rates of Na and Cl transport, b) the response to an individual absorptive stimulus (alanine, glucose, or epinephrine), and c) the response to a combination of the three absorptive stimuli. The results indicate that MP 1) increases basal absorption of Na and Cl and secretion of bicarbonate (as measured by residual ion flux), 2) does not alter the specific transport pathways stimulated by maximal doses of alanine, glucose, or epinephrine, but 3) significantly increases the absorptive capacity of ileum. After addition of combined alanine, glucose, and epinephrine, MP-treated ileum absorbed 15.8 mueq X cm-2 X h-1 Na (vs. 6.6 in controls, P less than 0.001) and 9.5 mueq X cm-2 X h-1 Cl (vs. 4.1 in controls, P less than 0.005). Additionally MP did not alter the Na dependence of either the short-circuit current or Cl absorption found in controls, although there appears to be a portion of residual ion flux insensitive to epinephrine inhibition. These data suggest that the MP-induced increase in absorptive capacity is due to an increase in a postapical transport step, most probably the Na pump.

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Regulation of ion transport across lamprey (Lampetra fluviatilis) erythrocyte membrane by oxygen tension

Journal of Experimental Biology ◽

10.1242/jeb.201.12.1927 ◽

1998 ◽

Vol 201 (12) ◽

pp. 1927-1937 ◽

Cited By ~ 2

Author(s):

LV Virkki ◽

A Salama ◽

M Nikinmaa

Keyword(s):

Ion Transport ◽

Erythrocyte Membrane ◽

Oxygen Tension ◽

Radioactive Isotope ◽

Marked Reduction ◽

Marked Effect ◽

Hypotonic Medium ◽

Lampetra Fluviatilis ◽

Transport Pathways ◽

Hypoxic Conditions

We have measured the effects of oxygen tension on the transport of Na+, K+ and Cl- across the erythrocyte membrane of the lamprey Lampetra fluviatilis. The transport of each ion was affected by the oxygen tension of the medium. Hypoxic conditions (PO2 2 kPa) caused an increase in the acidification-induced influx of Na+ via Na+/H+ exchange. The influx of K+ was only slightly affected by the oxygenation of the medium. In contrast, the basal K+ efflux, measured using the radioactive isotope 43K, was markedly reduced by decreasing the oxygen tension of the medium, whereas the K+ flux in hypotonic medium was not affected. Only minor effects of hypoxic conditions on the influx of Cl- were observed in either isotonic or hypotonic conditions (there was a tendency for the isotonic influx to increase) or on the efflux in isotonic conditions. However, deoxygenation caused a marked reduction in the Cl- efflux in hypotonic conditions. The results show that oxygen tension has a marked effect on the pH and volume regulatory transport pathways of lamprey erythrocytes. For K+ and Cl-, the regulation appears to be asymmetric, i.e. influx and efflux are affected differently.

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