Electrogenic sodium-bicarbonate symport in cultured corneal endothelial cells

Wiederholt, Michael; Jentsch, Thomas J.; Keller, Svea K.

doi:10.1007/bf00581801

Cited by 25 publications

(13 citation statements)

References 20 publications

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“…In the model, an electrogenic Na § pump is placed in the lateral membranes where it has been found in this tissue by several investigators using morphological staining techniques (Kaye & Tice, 1966;Tervo & Palkama, 1975;Leuenberger & Novikoff, 1984). Jentsch et al (1984aJentsch et al ( ,b, 1985aJentsch et al ( -c, 1988 and Wiederholt et al (1985) have provided considerable information, both from intracellular pH measurements and from microelectrode measurements in cultured bovine endothelium, which supports the proposed model. Key to those experiments was the finding that the normally steady membrane voltage transiently depolarized when HCO2 was removed from the bath and transiently hyperpolarized when it was returned.…”

Section: Discussionsupporting

confidence: 74%

“…While our experiments were not designed to test the models of fluid transport put forth by Fischbarg et al (1985), Jentsch, Keller, and Wiederholt (1985a), Widerholt, Jentsch and Keller (1985), and Lyslo et al (1985), the results in retrospect may prove useful in explaining some of the phenomena seen and predicted by these authors. These authors propose a similar transport scheme in which Na § entry is via an amiloride blockable Na+/H + exchanger in the basolateral membrane (see also Middlefart & Ratkje, 1985) duce COR which enters the cell directly through the membrane lipid.…”

Section: Discussionmentioning

confidence: 92%

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Potassium channel in rabbit corneal endothelium activated by external anions

et al. 1990

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The apical membrane of the rabbit corneal endothelium contains a potassium-selective ionic channel. In patch-clamp recordings, the probability of finding the channel in the open state (Po) depends on the presence of either HCO3- or Cl- in the bathing medium. In a methane sulfonate-containing bath, Po is less than 0.05 at all physiologically relevant transmembrane voltages. With 0 mM [HCO3-]o at +60 mV, Po was 0.085 and increased to 0.40 when [HCO3-]o was 15 mM. With 4 mM [Cl-]o at +60 mV, Po was 0.083 and with 150 mM Cl-, Po increased to 0.36. Low Po's are also found when propionate, sulphate, bromide, and nitrate are the primary bath anions. The mechanism of action of the anion-stimulated K+ channel gating is not yet known, but a direct action of pH seems unlikely. The alkalinization of cytoplasm associated with the addition of 10 mM (NH4)2SO4 to the bath and the acidification accompanying its removal do not result in channel activation nor does the use of Nigericin to equilibrate intracellular pH with that of the bath over the pH range of 6.8 to 7.8. Channel gating also is not affected by bathing the internal surface of the patch with cAMP, cGMP, GTP-gamma-s, Mg2+ or ATP. Blockers of Na/H+ exchange, Na(+)-HCO3- cotransport, Na(+)-K+ ATPase and carbonic anhydrase do not block the HCO3- stimulation of Po. Several of the properties of the channel could explain some of the previously reported voltage changes that occur in corneal endothelial cells stimulated by extracellular anions.

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Section: Discussionsupporting

confidence: 74%

Section: Discussionmentioning

confidence: 92%

Potassium channel in rabbit corneal endothelium activated by external anions

et al. 1990

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“…Working with a 1:2 stoichiometry (543) and importing HCO 3 Ϫ from the stroma (FIGURE 19) into the cell, NBCe1 in the corneal endothelium is in a position to make a substantial contribution to the basolateral step of transepithelial HCO 3 Ϫ secretion into the anterior chamber (i.e., aqueous humor). It is thought that this transcellular HCO 3 Ϫ movement drives fluid reabsorption from the stroma into the anterior chamber, thereby maintaining appropriate corneal hydration and transparency (579,922,923,1035). 42 The molecular mechanisms underlying this process (shown in FIGURE 19) are reviewed in Reference 96.…”

Section: Iii) Sensory Organs A) Transepithelial Hcomentioning

confidence: 99%

The Divergence, Actions, Roles, and Relatives of Sodium-Coupled Bicarbonate Transporters

Parker

Boron

2013

Physiological Reviews

246

262

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The mammalian Slc4 (Solute carrier 4) family of transporters is a functionally diverse group of 10 multi-spanning membrane proteins that includes three Cl-HCO3 exchangers (AE1-3), five Na(+)-coupled HCO3(-) transporters (NCBTs), and two other unusual members (AE4, BTR1). In this review, we mainly focus on the five mammalian NCBTs-NBCe1, NBCe2, NBCn1, NDCBE, and NBCn2. Each plays a specialized role in maintaining intracellular pH and, by contributing to the movement of HCO3(-) across epithelia, in maintaining whole-body pH and otherwise contributing to epithelial transport. Disruptions involving NCBT genes are linked to blindness, deafness, proximal renal tubular acidosis, mental retardation, and epilepsy. We also review AE1-3, AE4, and BTR1, addressing their relevance to the study of NCBTs. This review draws together recent advances in our understanding of the phylogenetic origins and physiological relevance of NCBTs and their progenitors. Underlying these advances is progress in such diverse disciplines as physiology, molecular biology, genetics, immunocytochemistry, proteomics, and structural biology. This review highlights the key similarities and differences between individual NCBTs and the genes that encode them and also clarifies the sometimes confusing NCBT nomenclature.

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“…Since 1983, the process has been described in rabbit proximal tubule (Biagi and Sohtell, 1986;Grass1 and Aronson, 1986;Sasaki et al, 1987;Soleimani et al, 19871, rat proximal tubule (Alpern, 1985;Yoshitomi et al, 19851, Necturus proximal tubule (Lopes et al, 19871, bovine corneal endothelium (Wiederholt et al, 1985), oxyntic cells of frog gastric fundus (Curci et al, 19871, and glial cells of the leech (Deitmer and Schlue, 1989).…”

Section: Discussion Results Of Conventional Microelectrode Studiesmentioning

confidence: 96%

Further studies of electrogenic Na⁺/HCO cotransport in glial cells of necturus optic nerve: Regulation of pH_i

Astion

Chvatal²,

Orkand

1991

Glia

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In the presence of Ba++, an increase in the bath HCO3- at constant CO2 (i.e., variable bath pH) produced a hyperpolarization. The hyperpolarizing effect of adding HCO3-/CO2 at constant bath pH was not significantly affected by the presence of 50 mumol/l strophanthidin. In the absence of Ba++, addition of HCO3-/CO2 at constant bath pH produced a Na(+)-dependent hyperpolarization. Therefore, CO2 movements, electrogenic Na+/K+ pump activity and changes in Ba++ binding do not contribute significantly to the hyperpolarization induced by HCO3-. These results along with the results of previous studies (Astion et al: J Gen Physiol 93:731, 1989) strongly suggest that the hyperpolarization induced by the addition of HCO3- is due to an electrogenic Na+/HCO3- cotransporter, which transports Na+, HCO3- (or its equivalent), and net negative charge across the glial membrane. To study the role of electrogenic Na+/HCO3- cotransport in the regulation of pHi in glial cells, we used intracellular double-barreled, pH-sensitive microelectrodes. At a bath pH of 7.5, the mean initial intracellular pH (pHi) was 7.32 (SD 0.03, n = 6) in HEPES-buffered Ringer's solution and 7.39 (SD 0.1, n = 6) in HCO3-/CO2 buffered solution. These values for pHi are more than 1.2 pH units alkaline to the pHi predicted from a passive distribution of protons; thus, these cells actively regulate pHi. Superfusion and withdrawal of 15 mmol/l NH4+ induced an acidification of 0.2 to 0.3 pH units, which recovered toward the original steady-state pHi.(ABSTRACT TRUNCATED AT 250 WORDS)

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Electrogenic sodium-bicarbonate symport in cultured corneal endothelial cells

Cited by 25 publications

References 20 publications

Potassium channel in rabbit corneal endothelium activated by external anions

Potassium channel in rabbit corneal endothelium activated by external anions

The Divergence, Actions, Roles, and Relatives of Sodium-Coupled Bicarbonate Transporters

Further studies of electrogenic Na⁺/HCO cotransport in glial cells of necturus optic nerve: Regulation of pH_i

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Electrogenic sodium-bicarbonate symport in cultured corneal endothelial cells

Cited by 25 publications

References 20 publications

Potassium channel in rabbit corneal endothelium activated by external anions

Potassium channel in rabbit corneal endothelium activated by external anions

The Divergence, Actions, Roles, and Relatives of Sodium-Coupled Bicarbonate Transporters

Further studies of electrogenic Na+/HCO cotransport in glial cells of necturus optic nerve: Regulation of pHi

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Further studies of electrogenic Na⁺/HCO cotransport in glial cells of necturus optic nerve: Regulation of pH_i