Use of niflumic acid to determine the nature of the asymmetry of the human erythrocyte anion exchange system.

Knauf, Philip A.; Mann, Neelam

doi:10.1085/jgp.83.5.703

Cited by 65 publications

(27 citation statements)

References 17 publications

(40 reference statements)

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“…Other work on erythrocytes has suggested that there are modulatory anion binding sites (Dalmark, 1976) and asymmetries in the system with respect either to the internal and external affinities or to the translocation rates in the two directions (e.g. Gunn & Frolich, 1979;Knauf, Law, Tarshis & Furuya, 1984;Knauf & Mann, 1984). Our results may also suggest, although not compellingly, that the mechanism is asymmetric.…”

Section: Selectivity Of CL Over Hco3supporting

confidence: 45%

The effects of bicarbonate and foreign anions on chloride transport in smooth muscle of the guinea‐pig vas deferens.

Aickin¹,

Brading²

1985

The Journal of Physiology

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SUMMARY1. The selectivity of the external site of the Cl transporting mechanism in the guinea-pig vas deferens has been investigated by measurement of 36Cl uptake and efflux and by direct measurement of intracellular pH.2. Replacing 50 % of the Cl in normal Krebs solution inhibited the 15 min uptake of 36C1 in the order NO3 > Br > SCN > F > I > glucuronate, both in Cl-depleted tissues and tissues pre-incubated in the 50 %-Cl solutions (steady-state uptake). After 3 h incubation in these solutions, the total cellular Cl was reduced by the anions in the order Br > NO3 > I > SCN > F > glucuronate. Br, NO3 and I reduced the cellular Cl to less than 50 % of normal, suggesting that they are actively taken up by the cells.3. The ability of foreign anions to inhibit a 3 min uptake of high specific activity, low concentration Cl (6-5 mM) suggests an apparent affinity series of NO3 > Cl = SCN = Br > I > F at the external site.4. Addition of NO3, Cl, Br, HCO3, F, SCN or I to a Cl-free, nominally HCO3-free bathing solution accelerated 36CI efflux. The first four mentioned were powerful stimulants, the other three less potent. However, the exact position of HCO3 in the sequence is uncertain. The rapidity with which CO2 crosses the membrane and forms HCO3 intracellularly may allow competition between HCO3 and Cl at the internal site and so distort the result. The action of F is also questionable since this ion drastically reduces the divalent cation activity and is a metabolic inhibitor.5. Measurement of intracellular pH provided conclusive evidence that Cl, NO3, Br and I can exchange with HCO3 across the cell membrane. This exchange is as rapid with NO3 as with Cl but slower with Br and considerably slower with I. The results also indicate that SCN ions cross the cell membrane.6. It is concluded that Cl, HCO3, Br and NO3 are all translocated by the exchange carrier. I and perhaps SCN also interact with the transport mechanism, but the translocation rate is then greatly reduced. The precise order of the affinity of these anions remains uncertain but the following sequence: NO3 > Cl = SCN = Br >

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Section: Selectivity Of CL Over Hco3supporting

confidence: 45%

The effects of bicarbonate and foreign anions on chloride transport in smooth muscle of the guinea‐pig vas deferens.

Aickin¹,

Brading²

1985

The Journal of Physiology

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“…Under the circumstances of the experiment in Table 111, however, niflumic acid should increase the fraction of Eo and ECIo by -2.8-fold, while decreasing the fraction of E; and ECl; by nearly half (calculated . assuming symmetric Cl-dissociation constants at the two sides of the membrane, as discussed in Knauf and Mann, 1984). Since niflumic acid has no significant effect on cation flux under these circumstances, it seems unlikely that the cation permeabilities of Eo and E; are markedly different and thus unlikely that the shift between these forms is of any importance in eliciting the increase in cation permeability .…”

Section: Mechanism Ofthe Cation Permeability Increasementioning

confidence: 95%

Mechanism of the increase in cation permeability of human erythrocytes in low-chloride media. Involvement of the anion transport protein capnophorin.

Jones¹,

Knauf²

1985

The Journal of General Physiology

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When human erythrocytes are suspended in low-Cl- media (with sucrose replacing Cl-), there is a large increase in both the net efflux and permeability of K+. A substantial portion (greater than 70% with Cl- less than 12.5 mM) of this K+ efflux is inhibited by the anion exchange inhibitor DIDS (4,4'-diisothiocyanostilbene-2,2'-disulfonic acid). This inhibition cannot be explained as an effect of DIDS on net Cl- permeability (Pcl) and membrane potential, but rather represents a direct effect on the K+ permeability. When cells are reacted with DIDS for different times, the inhibition of K+ efflux parallels that of Cl- exchange, which strongly indicates that the band 3 anion exchange protein (capnophorin) mediates the net K+ flux. Since a noncompetitive inhibitor of anion exchange, niflumic acid, has no effect on net K+ efflux, the net K+ flow does not seem to involve the band 3 conformational change that mediates anion exchange. The data suggest that in low-Cl- media, the anion selectivity of capnophorin decreases so that it can act as a very low-conductivity channel for cations. Na+ and Rb+, as well as K+, can utilize this pathway.

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“…Knauf & Mann, 1984;Gray & Ritchie, 1986;White & Aylwin, 1990;Hughes & Segawa, 1993;Janssen & Sims, 1993). We examined the effects of 100-200 gM niflumic acid on Ic, activated by GST (100 gM), and an example of strong reversible inhibition of GST-activated Ic, by 200 JiM niflumic acid is shown in Figure 3a.…”

Section: Cell Isolationmentioning

confidence: 99%

Activation of cardiac chloride conductance by the tyrosine kinase inhibitor, genistein

Shuba

Asai

Pelzer

et al. 1996

British J Pharmacology

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1 Genistein (GST), an inhibitor of protein tyrosine kinase (PTK), Na3VO4 (VO4), an inhibitor of phosphotyrosine phosphatase (PTPase), and forskolin (FSK), an activator of the cyclic AMP-dependent, cystic fibrosis transmembrane conductance regulator (CFTR) Cl-channel, were applied to guinea-pig ventricular myocytes to probe for a possible role of tyrosine phosphorylation in the regulation of cardiac Cl-channels. 2 Myocytes in the standard whole-cell configuration were pulsed to various potentials and Cl-current (Icl) measured as the difference from control background current. GST (1-500 gM) activated a current that had similar biophysical properties (time-and voltage-independent; Cl--dependent reversal potential and outward rectification) as Ick activated by 5 gM FSK. The EC_0 for activation of Cl-conductance (ga) by GST was approximately 100 JM, and g0 activated by GST (500 gM) was as large as gcj activated by maximally-effective FSK (5 gM). Daidzein, a GST analogue with little effect on PTK, was at least one order less effective than GST. 3 GST responses were rapidly and reversibly inhibited by 0.1-1 mM V04 treatments that had little effect on FSK-activated Icl.4 Niflumic acid (100-200 gM) reversibly depressed GST (100 uM)-activated gci by 55%. 5 GST (50 gM) strongly incremented current in myocytes with cyclic AMP-dependent CFTR IC, already activated by maximally-effective FSK 5 gM. 6 Based on these results, and on evidence of a synergistic interaction between GST and FSK, we conclude that inhibition of tyrosine phosphorylation by GST causes an activation of cardiac CFTR that is not mediated by an elevation of cyclic AMP.

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Use of niflumic acid to determine the nature of the asymmetry of the human erythrocyte anion exchange system.

Cited by 65 publications

References 17 publications

The effects of bicarbonate and foreign anions on chloride transport in smooth muscle of the guinea‐pig vas deferens.

The effects of bicarbonate and foreign anions on chloride transport in smooth muscle of the guinea‐pig vas deferens.

Mechanism of the increase in cation permeability of human erythrocytes in low-chloride media. Involvement of the anion transport protein capnophorin.

Activation of cardiac chloride conductance by the tyrosine kinase inhibitor, genistein

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