Network thermodynamic modeling of hormone regulation of active Na+ transport in cultured renal epithelium (A6)

1986 ◽  
Vol 250 (6) ◽  
pp. C978-C991 ◽  
Author(s):  
M. L. Fidelman ◽  
D. C. Mikulecky
Keyword(s):  
Steady State ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Hormone Regulation ◽  
Na Channels ◽  
Na Transport ◽  
Renal Epithelium ◽  
Ion Concentrations ◽  
Tight Junction Permeability

A network thermodynamic model was developed to describe steady-state ion flows (Na+,K+, and Cl-) and related electrical events in a cultured renal epithelium (A6) derived from toad kidney. Three hypotheses for explaining the steady-state increases in short-circuit current (SCC) produced by aldosterone and/or insulin were examined using the model. Changing only the number of basolateral Na+-K+ pumps produced virtually no change in SCC and was ruled out. Changing only the number of apical Na+ channels could produce sufficient increases in SCC but presented problems in the pattern of changes produced in cell ion concentrations and therefore appeared unlikely. Changing both apical and basolateral parameters in a balanced, coordinated manner produced the maximal changes in SCC with the minimal changes in cell ion concentrations and appeared to be the "best" hypothesis. In addition, it was found necessary for tight junction permeability to increase as active Na+ transport increased under open-circuit conditions. Simulations, using these results, compared favorably with experimental data on the stimulatory effects of aldosterone and insulin, both separately and together, on active Na+ transport.

Chronic regulation of transepithelial Na+ transport by the rate of apical Na+ entry

1996 ◽  
Vol 270 (2) ◽  
pp. C600-C607 ◽  
Author(s):  
M. D. Rokaw ◽  
E. Sarac ◽  
E. Lechman ◽  
M. West ◽  
J. Angeski ◽  
...  
Keyword(s):  
Short Circuit ◽  
Basolateral Membrane ◽  
Short Circuit Current ◽  
Maximal Activity ◽  
Na Channels ◽  
Na Transport ◽  
Bottom Structures ◽  
Stimulation Of

In several settings in vivo, prolonged inhibition of apical Na+ entry reduces and prolonged stimulation of apical entry enhances the ability of renal epithelial cells to reabsorb Na+, an important feature of the load-dependent regulation of renal tubular Na+ transport. To model this load dependency, apical Na+ entry was inhibited or stimulated for 18 h in A6 cells and vectorial transport was measured as short-circuit current (Isc) across monolayers on filter-bottom structures. Basal amiloride-sensitive Isc represents the activity of apical Na+ channels, whereas Isc after permeabilization of the apical membrane to cations with nystatin represents maximal activity of the basolateral Na(+)-K(+)-ATPase. Chronic inhibition of apical Na+ entry by 18-h apical exposure to amiloride or replacement of apical Na+ with tetramethylammonium (TMA+), followed by washing and restoration of normal apical medium, revealed a persistent decrease in Isc that remained despite exposure to nystatin. Both basal and nystatin-stimulated Isc recovered progressively after restoration of normal apical medium. In contrast, chronic stimulation of apical Na+ entry by short circuiting the epithelium increased Isc in the absence and presence of nystatin, indicating upregulation of both apical Na+ channels and basolateral Na(+)-K(+)-ATPase. Basolateral equilibrium [3H]ouabain binding was reduced to 67 +/- 5% in TMA+ vs. control cells, whereas values in 18-h short-circuited cells increased by 42 +/- 19%. The results demonstrate that load dependency of tubular Na+ transport can be modeled in vitro and indicate that the regulation of Na(+)-K(+)-ATPase observed in these studies occurs in part by changes in the density of functional transporter proteins within the basolateral membrane.

scholarly journals Amiloride-sensitive trypsinization of apical sodium channels. Analysis of hormonal regulation of sodium transport in toad bladder.

1983 ◽  
Vol 81 (6) ◽  
pp. 785-803 ◽  
Author(s):  
H Garty ◽  
I S Edelman
Keyword(s):  
Hormonal Regulation ◽  
Apical Membrane ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Toad Urinary Bladder ◽  
Apical Surface ◽  
Na Channels ◽  
Na Transport ◽  
Na Permeability ◽  
Trypsin Inhibition

Incubation of the mucosal surface of the toad urinary bladder with trypsin (1 mg/ml) irreversibly decreased the short-circuit current to 50% of the initial value. This decrease was accompanied by a proportionate decrease in apical Na permeability, estimated from the change in amiloride-sensitive resistance in depolarized preparations. In contrast, the paracellular resistance was unaffected by trypsinization. Amiloride, a specific blocker of the apical Na channels, prevented inactivation by trypsin. Inhibition of Na transport by substitution of mucosal Na, however, had no effect on the response to trypsin. Trypsinization of the apical membrane was also used to study regulation of Na transport by anti-diuretic hormone (ADH) and aldosterone. Prior exposure of the apical surface to trypsin did not reduce the response to ADH, which indicates that the ADH-induced Na channels were inaccessible to trypsin before addition of the hormone. On the other hand, stimulation of short-circuit current by aldosterone or pyruvate (added to substrate-depleted, aldosterone-repleted bladders) was substantially reduced by prior trypsinization of the apical surface. Thus, the increase in apical Na permeability elicited by aldosterone or substrate involves activation of Na channels that are continuously present in the apical membrane in nonconductive but trypsin-sensitive forms.

Modification of carboxyl of Na+ channel inhibits aldosterone action on Na+ transport

1983 ◽  
Vol 245 (6) ◽  
pp. F726-F734 ◽  
Author(s):  
J. Kipnowski ◽  
C. S. Park ◽  
D. D. Fanestil
Keyword(s):  
Amphotericin B ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Na Channel ◽  
Dependent Manner ◽  
Na Channels ◽  
Na Transport ◽  
Maximal Increase ◽  
Osmotic Water ◽  
Stimulation Of

We investigated the effect of the carboxyl-selective reagent N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) on aldosterone stimulation of Na+ transport in the urinary bladder of the toad. Na+ transport, measured as the short-circuit current (SCC), was irreversibly inhibited by EEDQ in a dose- and time-dependent manner prior to addition of aldosterone. The greater the percentage inhibition by EEDQ (X), the smaller was the maximal increase of SCC after aldosterone (Y). This relationship gave the regression equation Y = 128.41 - 1.73X, r = -0.99 (n = 35). Evidence that the inhibition of SCC produced by EEDQ was limited to effects at the mucosal membrane was attested by the following: 1) EEDQ did not alter the stimulation by aldosterone of the osmotic water flow response to antidiuretic hormone; 2) whereas inhibition of protein synthesis by cycloheximide prevented this effect of aldosterone; 3) amphotericin B fully restored SCC previously inhibited by EEDQ to the level produced in tissues not inhibited by EEDQ; 4) comparison of the effects of amiloride vs. EEDQ pretreatment on the SCC response to aldosterone and amphotericin B revealed nearly identical characteristics; 5) in contrast, amphotericin B stimulation of SCC was limited when Na+ transport was limited by antimycin A (an inhibitor of energy production) or by ouabain. The findings fail to provide positive evidence for the hypothesis that aldosterone induces the synthesis of new Na+ channels but are consistent with hormonal activation of previously existing but nonfunctioning Na+ channels.

Studies on locust rectum. III. Stimulation of electrogenic chloride transport by hemolymph

1980 ◽  
Vol 58 (10) ◽  
pp. 1933-1939 ◽  
Author(s):  
J. H. Spring ◽  
J. E. Phillips
Keyword(s):  
Steady State ◽  
Filter Paper ◽  
Chloride Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Simultaneous Measurements ◽  
Parallel Increase ◽  
Neuroendocrine Organ ◽  
Stimulation Of

Hemolymph was collected from recently fed desert locusts either by adsorption onto filter paper, or by centrifugation and methanol extraction. Whole hemolymph caused both the short-circuit current (Isc) and open-circuit transepithelial electropotential difference (PD) across locust recta mounted in Ussing-type chambers to double during the steady-state period. Methanol extracts of hemolymph caused similar but smaller increases in Isc. The transepithelial resistance (R) did not change. Simultaneous measurements of 36Cl− fluxes indicated that all of the increase in Isc following stimulation could be accounted for by a parallel increase in net Cl− absorption from the lumen side. With the exception of an initial small biphasic fluctuation in Isc, stimulation by hemolymph exhibited identical characteristics to those produced by submaximal dosages of corpora cardiaca (CC). Cardiatectomy drastically reduced the stimulatory activity of hemolymph, suggesting that this neuroendocrine organ is the source of the active factor (chloride transport stimulating hormone (CTSH)) in hemolymph.

scholarly journals Na Transport across Frog Skin at Low External Na Concentrations

1966 ◽  
Vol 49 (6) ◽  
pp. 1161-1176 ◽  
Author(s):  
THOMAS U. L. BIBER ◽  
RONALD A. CHEZ ◽  
PETER F. CURRAN
Keyword(s):  
Frog Skin ◽  
Short Circuit ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Potential Profile ◽  
Na Transport ◽  
Ringer’S Solution ◽  
Electrical Potentials ◽  
Single Compartment

Isolated frog skin was bathed with a dilute solution containing 1 mm NaCl on the outside and with normal Ringer’s solution on the inner surface. Net Na flux was determined by simultaneous measurement of unidirectional fluxes with Na22 and Na24 and intracellular electrical potentials were examined with microelectrodes. There was a net inward transport of Na under both open-circuit and short-circuit conditions. The short-circuit current was approximately 15% greater than the net Na flux; the discrepancy could be accounted for by a small outward flux of Cl. The electrical potential profile did not differ greatly from that observed in skins bathed on the outside with normal Ringer’s solution. Under open-circuit conditions, there were usually several potential steps and under short-circuit conditions the cells were negative relative to the bathing solutions. Estimates of epithelial Na concentrations utilizing radioactive Na suggested that if all epithelial Na were in a single compartment, an active entry step would be necessary to allow a net inward Na transport. The results could also be explained by a series arrangement of Na compartments without necessarily postulating an active Na entry. The behavior of the potential profile suggested that this latter alternative was more likely.

Transcellular sodium transport in cultured cystic fibrosis human nasal epithelium

1991 ◽  
Vol 261 (2) ◽  
pp. C332-C341 ◽  
Author(s):  
N. J. Willumsen ◽  
R. C. Boucher
Keyword(s):  
Cystic Fibrosis ◽  
Short Circuit ◽  
Ussing Chamber ◽  
Basolateral Membrane ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Na Transport ◽  
Airway Epithelia ◽  
Human Nasal Epithelium ◽  
Epithelial Cultures

Cystic fibrosis (CF) airway epithelia exhibit raised transepithelial Na+ transport rates, as determined by open-circuit isotope fluxes and estimates of the amiloride-sensitive equivalent short-circuit current (Ieq). To study the contribution of apical and basolateral membrane paths to raised Na+ transport in CF, CF nasal epithelial cultures were studied with double-barreled Na(+)-selective microelectrodes and the Ussing chamber technique. Intracellular Na+ activity (acNa) was 24.1 +/- 1.5 mM (n = 36), a value similar to acNa of normal nasal epithelial cells. Reduction of luminal [Na+] to 3 mM abolished Ieq and reduced acNa. Amiloride (10(-4) M) abolished Ieq but increased acNa from 20 +/- 2 to 36 +/- 7 mM (n = 10). Amiloride-induced increase in acNa was not affected by serosal [Na+] reduction but was blocked by preexposure to reduced luminal [Na+]. Amphotericin B increased Ieq during amiloride exposure, indicating that amiloride did not inhibit NA(+)-K(+)-ATPase. Ouabain abolished Ieq and slowly raised acNa. Reduction of serosal [Na+] led to a decrease in acNa that was blocked by bumetanide. It is concluded that 1) CF airway epithelia exhibit an increased apical membrane Na+ permeability, 2) acNa is regulated to a normal level in CF cells despite increased transcellular Na+ fluxes, 3) the abnormal increase in acNa in response to amiloride is dependent on luminal Na+, 4) Na+ is transported across the basolateral membrane by a bumetanide-sensitive cotransport mechanism, and 5) ouabain inhibits the basolateral Na(+)-K(+)-ATPase, causing slow dissipation of the chemical and electrical gradients across the cell membranes.

scholarly journals CdTe-Based Thin Film Solar Cells: Past, Present and Future

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1684
Author(s):  
Alessandro Romeo ◽  
Elisa Artegiani
Keyword(s):  
Thin Film ◽  
Solar Cells ◽  
Solar Cell ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Short Circuit Current Density ◽  
Open Circuit ◽  
Early Years ◽  
Solar Cell Efficiency ◽  
Cell Efficiency

CdTe is a very robust and chemically stable material and for this reason its related solar cell thin film photovoltaic technology is now the only thin film technology in the first 10 top producers in the world. CdTe has an optimum band gap for the Schockley-Queisser limit and could deliver very high efficiencies as single junction device of more than 32%, with an open circuit voltage of 1 V and a short circuit current density exceeding 30 mA/cm2. CdTe solar cells were introduced at the beginning of the 70s and they have been studied and implemented particularly in the last 30 years. The strong improvement in efficiency in the last 5 years was obtained by a new redesign of the CdTe solar cell device reaching a single solar cell efficiency of 22.1% and a module efficiency of 19%. In this paper we describe the fabrication process following the history of the solar cell as it was developed in the early years up to the latest development and changes. Moreover the paper also presents future possible alternative absorbers and discusses the only apparently controversial environmental impacts of this fantastic technology.

scholarly journals GaInP/GaAs/poly-Si Multi-Junction Solar Cells by in Metal Balls Bonding

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 726
Author(s):  
Ray-Hua Horng ◽  
Yu-Cheng Kao ◽  
Apoorva Sood ◽  
Po-Liang Liu ◽  
Wei-Cheng Wang ◽  
...  
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Low Temperature ◽  
Triple Junction ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Metal Line ◽  
Solar Simulator ◽  
Junction Solar Cell

In this study, a mechanical stacking technique has been used to bond together the GaInP/GaAs and poly-silicon (Si) solar wafers. A GaInP/GaAs/poly-Si triple-junction solar cell has mechanically stacked using a low-temperature bonding process which involves micro metal In balls on a metal line using a high-optical-transmission spin-coated glue material. Current–voltage measurements of the GaInP/GaAs/poly-Si triple-junction solar cells have carried out at room temperature both in the dark and under 1 sun with 100 mW/cm2 power density using a solar simulator. The GaInP/GaAs/poly-Si triple-junction solar cell has reached an efficiency of 24.5% with an open-circuit voltage of 2.68 V, a short-circuit current density of 12.39 mA/cm2, and a fill-factor of 73.8%. This study demonstrates a great potential for the low-temperature micro-metal-ball mechanical stacking technique to achieve high conversion efficiency for solar cells with three or more junctions.

scholarly journals Photocurrent density and electrical properties of Bi0.5Na0.5TiO3-BaNi0.5Nb0.5O3 ceramics

2021 ◽  
Author(s):  
Mingqiang Zhong ◽  
Qin Feng ◽  
Changlai Yuan ◽  
Xiao Liu ◽  
Baohua Zhu ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Photovoltaic Effect ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Photocurrent Density ◽  
Open Circuit ◽  
Light Conditions ◽  
X Ray Diffraction ◽  
Solid State Method ◽  
X Ray

AbstractIn this work, the (1−x)Bi0.5Na0.5TiO3-xBaNi0.5Nb0.5O3 (BNT-BNN; 0.00 ⩽ x ⩽ 0.20) ceramics were prepared via a high-temperature solid-state method. The crystalline structures, photovoltaic effect, and electrical properties of the ceramics were investigated. According to X-ray diffraction, the system shows a single perovskite structure. The samples show the normal ferroelectric loops. With the increase of BNN content, the remnant polarization (Pr) and coercive field (Ec) decrease gradually. The optical band gap of the samples narrows from 3.10 to 2.27 eV. The conductive species of grains and grain boundaries in the ceramics are ascribed to the double ionized oxygen vacancies. The open-circuit voltage (Voc) of ∼15.7 V and short-circuit current (Jsc) of ∼1450 nA/cm2 are obtained in the 0.95BNT-0.05BNN ceramic under 1 sun illumination (AM1.5G, 100 mW/cm2). A larger Voc of 23 V and a higher Jsc of 5500 nA/cm2 are achieved at the poling field of 60 kV/cm under the same light conditions. The study shows this system has great application prospects in the photovoltaic field.

scholarly journals Ultrathin Cu(In,Ga)Se2 Solar Cells with Ag/AlOx Passivating Back Reflector

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4268
Author(s):  
Jessica de Wild ◽  
Gizem Birant ◽  
Guy Brammertz ◽  
Marc Meuris ◽  
Jef Poortmans ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Solar Cells ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Short Circuit Current Density ◽  
Open Circuit ◽  
Electron Microscopic ◽  
Current Increase ◽  
Time Resolved ◽  
Cigs Solar Cells

Ultrathin Cu(In,Ga)Se2 (CIGS) absorber layers of 550 nm were grown on Ag/AlOx stacks. The addition of the stack resulted in solar cells with improved fill factor, open circuit voltage and short circuit current density. The efficiency was increased from 7% to almost 12%. Photoluminescence (PL) and time resolved PL were improved, which was attributed to the passivating properties of AlOx. A current increase of almost 2 mA/cm2 was measured, due to increased light scattering and surface roughness. With time of flight—secondary ion mass spectroscopy, the elemental profiles were measured. It was found that the Ag is incorporated through the whole CIGS layer. Secondary electron microscopic images of the Mo back revealed residuals of the Ag/AlOx stack, which was confirmed by energy dispersive X-ray spectroscopy measurements. It is assumed to induce the increased surface roughness and scattering properties. At the front, large stains are visible for the cells with the Ag/AlOx back contact. An ammonia sulfide etching step was therefore applied on the bare absorber improving the efficiency further to 11.7%. It shows the potential of utilizing an Ag/AlOx stack at the back to improve both electrical and optical properties of ultrathin CIGS solar cells.

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