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The K-Cl cotranspor...
The K-Cl cotransporter in the lobster stretch receptor neurone-a kinetic analysis.
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- Fåhraeus, C (författare)
- Lund University,Lunds universitet,Hjärnans sensorimotoriska funktioner,Forskargrupper vid Lunds universitet,Neural Basis of Sensorimotor Control,Lund University Research Groups
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Theander, S (författare)
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Edman, A (författare)
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- Grampp, Wolfgang (författare)
- Lund University,Lunds universitet,Neurofysiologi,Forskargrupper vid Lunds universitet,Neurophysiology,Lund University Research Groups
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(creator_code:org_t)
- Elsevier BV, 2002
- 2002
- Engelska.
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Ingår i: Journal of Theoretical Biology. - : Elsevier BV. - 1095-8541 .- 0022-5193. ; 217:3, s. 287-309
- Relaterad länk:
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http://www.ncbi.nlm....
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http://dx.doi.org/10...
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https://lup.lub.lu.s...
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https://doi.org/10.1...
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Abstract
Ämnesord
Stäng
- Experiments were performed to define quantitatively the substrate (K(+) and Cl(-)) dependence of the transport function (production of equally large and oppositely directed K(+)and Cl(-) flows/currents) of an earlier (Theander et al., 1999) identified electroneutral K-Cl cotransporter in the slowly adapting stretch receptor neurone of the European lobster. The experiments were based on microelectrode techniques. This allowed us to perform steady-state measurements of the so-called "instantaneous" current-voltage relationships (around a holding voltage of -65 mV after a blockage of the cell's action potential and hyperpolarization-activated currents) and intracellular ion concentrations at various settings of the extracellular K(+) and Cl(-) concentrations. From the results, we could then define steady-state values of all of the cell's non-KCl cotransporter K(+) and Cl(-) currents. Finally, the negative sums of the inferred non-KCl cotransporter K(+) and Cl(-) currents could be taken as equivalents of the K-Cl cotransporter's K(+) and Cl(-) currents for the reason that, in steady state, all membrane currents add up to zero. For the cotransporter currents, thus inferred for a range from 2.5/410.5 to 40.0/448.0 mM external K(+)/Cl(-), we found that their absolute values increased in a nonlinear fashion from about 5 nA cell(-1) at the lowest, to about 20 nA cell(-1) at the highest external K(+)/Cl(-) concentrations. Formally, this relationship could be reproduced by a Hill function-based enzyme kinetic expression simulating inward and outward transmembrane electroneutral ion transports. Following insertion of this expression into a comprehensive model of electrical membrane functions and intracellular solute and solvent control in the lobster stretch receptor neurone, the model predictions suggested that the K-Cl cotransporter does play an important role in (a) keeping intracellular Cl(-) low for a proper function of the cell's inhibitory system, and (b) enabling rapid transmembrane K(+) shifts that provide for a stabilization of the cell's membrane voltage and membrane excitability in cases of varying extracellular K(+) concentrations. The model predictions gave, however, no clear evidence that the K-Cl cotransporter is critically involved in the cell's volume regulation in conditions of varying extracellular osmolalities.
Ämnesord
- MEDICIN OCH HÄLSOVETENSKAP -- Medicinska och farmaceutiska grundvetenskaper -- Neurovetenskaper (hsv//swe)
- MEDICAL AND HEALTH SCIENCES -- Basic Medicine -- Neurosciences (hsv//eng)
Nyckelord
- Experiments were performed to define quantitatively the substrate (K(+) and Cl(-)) dependence of the transport function (production of equally large and oppositely directed K(+)and Cl(-) flows/currents) of an earlier (Theander et al.
- 1999) identified electroneutral K-Cl cotransporter in the slowly adapting stretch receptor neurone of the European lobster. The experiments were based on microelectrode techniques. This allowed us to perform steady-state measurements of the so-called "instantaneous" current-voltage relationships (around a holding voltage of -65 mV after a blockage of the cell's action potential and hyperpolarization-activated currents) and intracellular ion concentrations at various settings of the extracellular K(+) and Cl(-) concentrations. From the results
- we could then define steady-state values of all of the cell's non-KCl cotransporter K(+) and Cl(-) currents. Finally
- the negative sums of the inferred non-KCl cotransporter K(+) and Cl(-) currents could be taken as equivalents of the K-Cl cotransporter's K(+) and Cl(-) currents for the reason that
- in steady state
- all membrane currents add up to zero. For the cotransporter currents
- thus inferred for a range from 2.5/410.5 to 40.0/448.0 mM external K(+)/Cl(-)
- we found that their absolute values increased in a nonlinear fashion from about 5 nA cell(-1) at the lowest
- to about 20 nA cell(-1) at the highest external K(+)/Cl(-) concentrations. Formally
- this relationship could be reproduced by a Hill function-based enzyme kinetic expression simulating inward and outward transmembrane electroneutral ion transports. Following insertion of this expression into a comprehensive model of electrical membrane functions and intracellular solute and solvent control in the lobster stretch receptor neurone
- the model predictions suggested that the K-Cl cotransporter does play an important role in (a) keeping intracellular Cl(-) low for a proper function of the cell's inhibitory system
- and (b) enabling rapid transmembrane K(+) shifts that provide for a stabilization of the cell's membrane voltage and membrane excitability in cases of varying extracellular K(+) concentrations. The model predictions gave
- however
- no clear evidence that the K-Cl cotransporter is critically involved in the cell's volume regulation in conditions of varying extracellular osmolalities.
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