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Net charge transport during sodium-dependent calcium extrusion in isolated salamander rod outer segments

The light-sensitive current and the current associated with the extrusion of internal Ca2+ in exchange for external Na+ have been recorded from detached rod outer segments from the salamander retina by the use of the whole-cell voltage clamp technique. No significant current-carrying mechanisms are...

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Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 1991
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2229058/
https://www.ncbi.nlm.nih.gov/pubmed/1722238
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description The light-sensitive current and the current associated with the extrusion of internal Ca2+ in exchange for external Na+ have been recorded from detached rod outer segments from the salamander retina by the use of the whole-cell voltage clamp technique. No significant current-carrying mechanisms are present in the outer segment membrane apart from the light-sensitive conductance and the Na:Ca,K exchange, and exchange currents can therefore be recorded directly without the use of subtraction procedures or pharmacological blockers. The charge moved by the exchange was studied by loading outer segments with a known amount of calcium and then recording the exchange current on return to a Na(+)-containing solution. Calcium is not sequestered to any significant extent in a slowly exchanging internal store, as the charge recovered is unaffected if admission of the Na(+)-containing solution is delayed for 40 s. The number of charges flowing into the cell in exchange for each Ca2+ ion extruded was found not to deviate significantly from one over a wide range of ionic conditions and membrane potentials. These results show that the stoichiometry of the exchange is fixed over a wide range of conditions, and that the size of the inward exchange current is therefore directly proportional to the rate of Ca2+ efflux through the carrier.
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spelling pubmed-22290582008-04-23 Net charge transport during sodium-dependent calcium extrusion in isolated salamander rod outer segments J Gen Physiol Articles The light-sensitive current and the current associated with the extrusion of internal Ca2+ in exchange for external Na+ have been recorded from detached rod outer segments from the salamander retina by the use of the whole-cell voltage clamp technique. No significant current-carrying mechanisms are present in the outer segment membrane apart from the light-sensitive conductance and the Na:Ca,K exchange, and exchange currents can therefore be recorded directly without the use of subtraction procedures or pharmacological blockers. The charge moved by the exchange was studied by loading outer segments with a known amount of calcium and then recording the exchange current on return to a Na(+)-containing solution. Calcium is not sequestered to any significant extent in a slowly exchanging internal store, as the charge recovered is unaffected if admission of the Na(+)-containing solution is delayed for 40 s. The number of charges flowing into the cell in exchange for each Ca2+ ion extruded was found not to deviate significantly from one over a wide range of ionic conditions and membrane potentials. These results show that the stoichiometry of the exchange is fixed over a wide range of conditions, and that the size of the inward exchange current is therefore directly proportional to the rate of Ca2+ efflux through the carrier. The Rockefeller University Press 1991-09-01 /pmc/articles/PMC2229058/ /pubmed/1722238 Text en This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).
spellingShingle Articles
Net charge transport during sodium-dependent calcium extrusion in isolated salamander rod outer segments
title Net charge transport during sodium-dependent calcium extrusion in isolated salamander rod outer segments
title_full Net charge transport during sodium-dependent calcium extrusion in isolated salamander rod outer segments
title_fullStr Net charge transport during sodium-dependent calcium extrusion in isolated salamander rod outer segments
title_full_unstemmed Net charge transport during sodium-dependent calcium extrusion in isolated salamander rod outer segments
title_short Net charge transport during sodium-dependent calcium extrusion in isolated salamander rod outer segments
title_sort net charge transport during sodium-dependent calcium extrusion in isolated salamander rod outer segments
topic Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2229058/
https://www.ncbi.nlm.nih.gov/pubmed/1722238