Na-H and Cl-HCO3 exchange in rabbit oxyntic cells using fluorescence microscopy

Paradiso, Anthony M.; Tsien, Roger Y.; Demarest, J. R.; Machen, Terry E.

doi:10.1152/ajpcell.1987.253.1.c30

Cited by 64 publications

(21 citation statements)

References 17 publications

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“…In the histamine-stimulated cells, when it is expected that the Cl channels in the apical membrane have been activated (Demarest et al, 1989), there was still good agreement between the Cl fluxes (70 mM/min) and the HCO3 fluxes (77 mM/min). In addition, it has been shown previously that 200-500 ,uM H2DIDS largely blocks the Cl-induced changes of pHi (Paradiso et al, 1987), and the present experiments have shown that Cl fluxes were blocked by -80% (Figure 9). The close agreement among these measurements indicates that during changes of Clo, influx and efflux of Cl from the cell are mediated primarily through the anion exchanger that is present in the basolateral membrane.…”

Section: Discussionsupporting

confidence: 83%

“…Intracellular signaling events ultimately lead to the transition from the resting to the stimulated state. An H/ K-ATPase is activated in parallel with permeability pathways for both Cl and K on the apical canalicular face of the PC, whereas an anion exchanger provides pathways for Cl entry and HCO3 exit on the basolateral side of the cell (Ito and Schofield, 1974;Lee et al, 1979;Forte et al, 1981;Wolosin and Forte, 1984;Muallem et al, 1985Muallem et al, , 1988Paradiso et al, 1987; Ueda et al, 1987).…”

Section: Introductionmentioning

confidence: 99%

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Regulation of Cl/HCO3 exchange in gastric parietal cells.

Thomas

Machen

1991

Cell Regul

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Microspectrofluorimetry of the fluorescent indicators 2',7'-bis-(2-carboxyethyl)-5(and-6)carboxyfluorescein and 6-methoxy-N -(3-sulfopropyl) -quinolinium was used to measure intracellular pH (pHi), intracellular Cl (Cli), and transmembrane fluxes of HCO3 and Cl in single parietal cells (PC) in isolated rabbit gastric glands incubated in HCOJ C02-buffered solutions. Steady-state pHi was 7.2 in both resting (50 MM cimetidine) and stimulated (100 ,uM histamine) PCs. Transmembrane anion (HCO3 or Cl) flux rates during Cl removal from or readdition to the perfusate were the same in resting and stimulated PCs. These rates increased at alkaline pHi, though this pHi dependence was small in the physiological range. Maximum velocity (Vm,aJ for Cl influx or HCO3 effiux was 80-110 mM/min at pHi 7.6-7.8, and the Km for extracellular concentrations of Cl (Clo) was 25 mM; in the physiological range (pHi 7.1-7.3), V,,,. for anion fluxes was _50 mM/min. Steady-state Cli in the unstimulated PC was 62 ± 5 mM, but on histamine stimulation, Cli decreased rapidly to 25 mM and then increased back to a steady-state level of 44 mM. HCO3 fluxes due to Cl removal or readdition were completely blocked by 0.5 mM 4,4'-diisothiocyanatodihydrostilbene-2,2'-disulfonic acid (H2DIDS), but Cl fluxes were only inhibited by 80%. H2DIDS did not inhibit the decrease in Cli that occurred with histamine treatment. Diphenylamine carboxylate (0.5 mM) inhibited Cl flux by only 50% and caused no additional inhibition of Cl flux when used in conjunction with H2DIDS. Transmembrane anion fluxes during solution Cl removal or readdition occurred 80% through the anion exchanger at the basal membrane and 20% through other pathway(s), presumably the Cl channel in the apical membrane. We conclude that the increase in transport activity via the CI/HCO3 exchanger that occurs during histamine-induced increases in HCI secretion is due mostly to the decrease in Cli. In the resting cell with Cli = 62 mM, Clo = 120 mM, pHi = 7.2, and extracellular pH = 7.4, the anion exchanger is poised near its thermodynamic equilibrium. During histamine stimulation Cli drops from 62 mM to 44 mM, the thermodynamic equilibrium of the anion exchanger at the basolateral membrane is disturbed, and the anion exchanger then exchanges cellular HCO3 for extracellular Cl. Cli serves a crucial regulatory role in stimulus-secretion coupling in the PC.

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Section: Discussionsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Regulation of Cl/HCO3 exchange in gastric parietal cells.

Thomas

Machen

1991

Cell Regul

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“…However EBF was 28 pmol/min per mm in HCO , which was similar to the result obtained in Hepes. Therefore, exogenous HCO-failed to stimulate apical CF/ base exchange in contrast to the stimulation of Cl-/base exchange by HCO-reported in other cell types (15,16,(43)(44)(45)(46)(47). The lack of stimulation of apical Cl -/base exchange could have been due to enhanced basolateral base efflux in HCO--containing solutions.…”

Section: Discussioncontrasting

confidence: 60%

Mechanism of apical and basolateral Na(+)-independent Cl-/base exchange in the rabbit superficial proximal straight tubule.

Kurtz

Nagami²,

Yanagawa³

et al. 1994

J. Clin. Invest.

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The present study was undertaken to determine the magnitude and mechanism of base transport via the apical and basolateral Na '-independent Cl -/base exchangers in rabbit isolated perfused superficial S2 proximal tubules. The results demonstrate that there is an apical Na '-independent Cl-/ base exchanger on both membranes. HCO3 fails to stimulate apical Cl-/base exchange in contrast to the basolateral exchanger. Inhibition of endogenous HCO3 production does not alter the rate of apical Cl-/base exchange in Hepesbuffered solutions. Both exchangers are inhibited by H2DIDS and furosemide; however, the basolateral anion exchanger is more sensitive to these inhibitors. The results indicate that the apical and basolateral Cl-/base exchangers differ in their transport properties and are able to transport base equivalents in the absence of formate. The formate concentration in rabbit arterial serum is -6 ,uM and in vitro tubule formate production is < 0.6 pmol/min per mm.Formate in the micromolar range stimulates Jv in a dosedependent manner in the absence of a transepithelial Na+ and Cl-gradient and without a measurable effect on Cl--induced equivalent base flux. Apical formic acid recycling cannot be an important component of any cell model, which accounts for formic acid stimulation of transcellular NaCl transport in the rabbit superficial S2 proximal tubule. We propose that transcellular NaCl transport in this nephron segment is mediated by an apical Na+/H+ exchanger in parallel with a Cl-/OH-exchanger and that the secreted H+ and OH -ions form H20 in the tubule lumen. (J. Clin. Invest. 1994. 94:173-183.) Key words: Na+/H+ exchange-

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“…G astric acid production originates in the parietal cell through the coordinated operation of apical and basolateral membrane transport proteins (1)(2)(3)(4)(5)(6)(7)(8)(9). The apical secretory machinery includes the gastric H-K-ATPase, a chloride channel, and a K ϩ recycling pathway (1)(2)(3)(4)(5)(6)(7)(8)(9).…”

mentioning

confidence: 99%

“…The apical secretory machinery includes the gastric H-K-ATPase, a chloride channel, and a K ϩ recycling pathway (1)(2)(3)(4)(5)(6)(7)(8)(9). Despite an essential role for the apical Cl Ϫ channel in gastric acid secretion, its molecular identity remains unknown.…”

mentioning

confidence: 99%