Anion-selectivity of the Swelling-activated Osmolyte Channel in Eel Erythrocytes |
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Authors: | RA Lewis JDH Bursell K Kirk |
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Institution: | (1) University Laboratory of Physiology, Parks Rd, Oxford OX1 3PT, United Kingdom, GB |
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Abstract: | Osmotic swelling of fish erythrocytes activates a broad-specificity permeation pathway that mediates the volume-regulatory
efflux of taurine and other intracellular osmolytes. This pathway is blocked by inhibitors of the erythrocyte band 3 anion
exchanger, raising the possibility that band 3 is involved in the volume-regulatory response. In this study of eel erythrocytes,
a quantitative comparison of the pharmacology of swelling-activated taurine transport with that of band 3-mediated SO2−
4 transport showed there to be significant differences between them. N-ethylmaleimide and quinine were effective inhibitors of swelling-activated taurine transport but caused little, if any, inhibition
of band 3. Conversely, DIDS was a more potent inhibitor of band 3-mediated SO2−
4 flux than of swelling-activated taurine transport. In cells in isotonic medium, pretreated then co-incubated with 0.1 mm DIDS, the band 3-mediated transport of SO2−
4 and Cl− was reduced to a low level. Exposure of these cells to a hypotonic medium containing 0.1 mm DIDS was followed by the activation of a Cl− permeation pathway showing the same inhibitor sensitivity as swelling-activated taurine transport. The data are consistent
with swelling-activated transport of taurine and Cl− being via a common pathway. A comparison of the swelling-activated transport rates for taurine and Cl− with those for several other solutes was consistent with the hypothesis that this pathway is an anion-selective channel,
similar to those that mediate the volume-regulatory efflux of Cl− and organic osmolytes from mammalian cells.
Received: 7 July 1995/Revised: 2 September 1995 |
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Keywords: | : Taurine — Anion channel — Osmolyte — Volume regulation |
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