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Ion trapping with fast-response ion-selective microelectrodes enhances detection of extracellular ion channel gradients

Ion trapping with fast-response ion-selective microelectrodes enhances detection of extracellular ion channel gradients
Ion trapping with fast-response ion-selective microelectrodes enhances detection of extracellular ion channel gradients
Previously, functional mapping of channels has been achieved by measuring the passage of net charge and of specific ions with electrophysiological and intracellular fluorescence imaging techniques. However, functional mapping of ion channels using extracellular ion-selective microelectrodes has distinct advantages over the former methods. We have developed this method through measurement of extracellular K+ gradients caused by efflux through Ca2+-activated K+ channels expressed in Chinese hamster ovary cells. We report that electrodes constructed with short columns of a mechanically stable K+-selective liquid membrane respond quickly and measure changes in local [K+] consistent with a diffusion model. When used in close proximity to the plasma membrane (<4 µm), the ISMs pose a barrier to simple diffusion, creating an ion trap. The ion trap amplifies the local change in [K+] without dramatically changing the rise or fall time of the [K+] profile. Measurement of extracellular K+ gradients from activated rSlo channels shows that rapid events, 10–55 ms, can be characterized. This method provides a noninvasive means for functional mapping of channel location and density as well as for characterizing the properties of ion channels in the plasma membrane.
0006-3495
1597-1605
Messerli, Mark A.
94a8bd34-95d7-4a52-b4d8-1ccded0e8fe7
Collis, Leon P.
66f825a3-f4a7-4e85-a1ca-ee16497b8a81
Smith, Peter J.S.
003de469-9420-4f12-8f0e-8e8d76d28d6c
Messerli, Mark A.
94a8bd34-95d7-4a52-b4d8-1ccded0e8fe7
Collis, Leon P.
66f825a3-f4a7-4e85-a1ca-ee16497b8a81
Smith, Peter J.S.
003de469-9420-4f12-8f0e-8e8d76d28d6c

Messerli, Mark A., Collis, Leon P. and Smith, Peter J.S. (2009) Ion trapping with fast-response ion-selective microelectrodes enhances detection of extracellular ion channel gradients. Biophysical Journal, 96 (4), 1597-1605. (doi:10.1016/j.bpj.2008.11.025). (PMID:19217875)

Record type: Article

Abstract

Previously, functional mapping of channels has been achieved by measuring the passage of net charge and of specific ions with electrophysiological and intracellular fluorescence imaging techniques. However, functional mapping of ion channels using extracellular ion-selective microelectrodes has distinct advantages over the former methods. We have developed this method through measurement of extracellular K+ gradients caused by efflux through Ca2+-activated K+ channels expressed in Chinese hamster ovary cells. We report that electrodes constructed with short columns of a mechanically stable K+-selective liquid membrane respond quickly and measure changes in local [K+] consistent with a diffusion model. When used in close proximity to the plasma membrane (<4 µm), the ISMs pose a barrier to simple diffusion, creating an ion trap. The ion trap amplifies the local change in [K+] without dramatically changing the rise or fall time of the [K+] profile. Measurement of extracellular K+ gradients from activated rSlo channels shows that rapid events, 10–55 ms, can be characterized. This method provides a noninvasive means for functional mapping of channel location and density as well as for characterizing the properties of ion channels in the plasma membrane.

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Published date: 18 February 2009
Organisations: University of Southampton

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Local EPrints ID: 188759
URI: http://eprints.soton.ac.uk/id/eprint/188759
ISSN: 0006-3495
PURE UUID: a179c0d6-19cf-4c85-b1c9-f586d9f82a98
ORCID for Peter J.S. Smith: ORCID iD orcid.org/0000-0003-4400-6853

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Date deposited: 27 May 2011 15:42
Last modified: 19 Nov 2019 01:39

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Author: Mark A. Messerli
Author: Leon P. Collis

University divisions

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