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Cl- transport in the lobster stretch receptor neurone

Theander, S ; Edman, A ; Fåhraeus, C LU ; Akoev, G N and Grampp, W (1999) In Acta Physiologica Scandinavica 167(4). p.98-285
Abstract

Experiments were performed to identify mechanisms underlying non-leakage and non-H+/HCO3--linked transmembrane Cl- transports in the slowly adapting stretch receptor neurone of the European lobster, using intracellular microelectrode and pharmacological techniques. In methodological tests, it was established that direct estimates of intracellular Cl- with ion-sensitive microelectrodes are statistically identical with indirect estimates by means of a GABA method, where 1-2 mM GABA is transforming the cell's membrane voltage into its Cl- equilibrium voltage from which the Cl- concentration is inferred by the Nernst equation. From experiments using sodium orthovanadate and ethacrynic acid, supposed to block primary Cl- pumps, and... (More)

Experiments were performed to identify mechanisms underlying non-leakage and non-H+/HCO3--linked transmembrane Cl- transports in the slowly adapting stretch receptor neurone of the European lobster, using intracellular microelectrode and pharmacological techniques. In methodological tests, it was established that direct estimates of intracellular Cl- with ion-sensitive microelectrodes are statistically identical with indirect estimates by means of a GABA method, where 1-2 mM GABA is transforming the cell's membrane voltage into its Cl- equilibrium voltage from which the Cl- concentration is inferred by the Nernst equation. From experiments using sodium orthovanadate and ethacrynic acid, supposed to block primary Cl- pumps, and bumetanide, supposed to block Na-K-Cl co-transporters, it appeared that neither of the two Cl- transport systems exists in the stretch receptor neurone. It could be shown, however, that the cell is equipped with an electroneutral K-Cl co-transporter that (a) is blockable by furosemide in high (Km approximately 350 microM), by 4-acetamido-4'-isothiocyanato-stilbene-2,2-disulphonic acid (SITS) in medium-high (Km approximately 35 microM), and by 4, 4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS) in low (Km approximately 15 microM) doses, (b) is (transiently) activatable by (1 mM) n-ethylmaleimide, (c) is not suppressed by extracellular Rb+ or NH4+, and (d) is not directly coupled to any transmembrane transports of Na+, H+ or HCO3-. From functional tests, with varying transmembrane K+ and Cl- gradients, evidence obtained that the K-Cl co-transporter is able to reverse its transport direction and to adjust its transport rate in a considerable range. As a whole, the results speak in favour of the K-Cl co-transporter being responsible (a) for normally keeping the intracellular Cl- concentration at low levels, for an optimization of the cell's inhibitory system, and (b) for achieving fast transmembrane shifts of K+ (and Cl-), as a means of stabilizing the cell's membrane excitability in conditions of varying extracellular K+ concentrations.

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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Animals, Carrier Proteins/metabolism, Chlorides/metabolism, Ion Pumps/metabolism, Ion Transport, Mechanoreceptors/metabolism, Nephropidae, Neurons/metabolism, Potassium/metabolism, Sodium-Potassium-Chloride Symporters, Symporters
in
Acta Physiologica Scandinavica
volume
167
issue
4
pages
14 pages
publisher
Wiley-Blackwell
external identifiers
  • pmid:10632628
ISSN
0001-6772
DOI
10.1046/j.1365-201x.1999.00616.x
language
English
LU publication?
yes
id
f41f9784-e3f7-4f22-bd97-0f7b119d605d
date added to LUP
2018-12-13 14:12:16
date last changed
2020-12-11 04:12:59
@article{f41f9784-e3f7-4f22-bd97-0f7b119d605d,
  abstract     = {<p>Experiments were performed to identify mechanisms underlying non-leakage and non-H+/HCO3--linked transmembrane Cl- transports in the slowly adapting stretch receptor neurone of the European lobster, using intracellular microelectrode and pharmacological techniques. In methodological tests, it was established that direct estimates of intracellular Cl- with ion-sensitive microelectrodes are statistically identical with indirect estimates by means of a GABA method, where 1-2 mM GABA is transforming the cell's membrane voltage into its Cl- equilibrium voltage from which the Cl- concentration is inferred by the Nernst equation. From experiments using sodium orthovanadate and ethacrynic acid, supposed to block primary Cl- pumps, and bumetanide, supposed to block Na-K-Cl co-transporters, it appeared that neither of the two Cl- transport systems exists in the stretch receptor neurone. It could be shown, however, that the cell is equipped with an electroneutral K-Cl co-transporter that (a) is blockable by furosemide in high (Km approximately 350 microM), by 4-acetamido-4'-isothiocyanato-stilbene-2,2-disulphonic acid (SITS) in medium-high (Km approximately 35 microM), and by 4, 4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS) in low (Km approximately 15 microM) doses, (b) is (transiently) activatable by (1 mM) n-ethylmaleimide, (c) is not suppressed by extracellular Rb+ or NH4+, and (d) is not directly coupled to any transmembrane transports of Na+, H+ or HCO3-. From functional tests, with varying transmembrane K+ and Cl- gradients, evidence obtained that the K-Cl co-transporter is able to reverse its transport direction and to adjust its transport rate in a considerable range. As a whole, the results speak in favour of the K-Cl co-transporter being responsible (a) for normally keeping the intracellular Cl- concentration at low levels, for an optimization of the cell's inhibitory system, and (b) for achieving fast transmembrane shifts of K+ (and Cl-), as a means of stabilizing the cell's membrane excitability in conditions of varying extracellular K+ concentrations.</p>},
  author       = {Theander, S and Edman, A and Fåhraeus, C and Akoev, G N and Grampp, W},
  issn         = {0001-6772},
  language     = {eng},
  number       = {4},
  pages        = {98--285},
  publisher    = {Wiley-Blackwell},
  series       = {Acta Physiologica Scandinavica},
  title        = {Cl- transport in the lobster stretch receptor neurone},
  url          = {http://dx.doi.org/10.1046/j.1365-201x.1999.00616.x},
  doi          = {10.1046/j.1365-201x.1999.00616.x},
  volume       = {167},
  year         = {1999},
}