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Intracellular calcium buffering capacity in isolated squid axons

Changes in ionized calcium were studied in axons isolated from living squid by measuring absorbance of the Ca binding dye Arsenazo III using multiwavelength differential absorption spectroscopy. Absorption changes measured in situ were calibrated in vitro with media of ionic composition similar to a...

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Detalles Bibliográficos
Autores principales: Brinley, FJ, Tiffert, T, Scarpa, A, Mullins, LJ
Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 1977
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2228465/
https://www.ncbi.nlm.nih.gov/pubmed/894260
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author Brinley, FJ
Tiffert, T
Scarpa, A
Mullins, LJ
author_facet Brinley, FJ
Tiffert, T
Scarpa, A
Mullins, LJ
author_sort Brinley, FJ
collection PubMed
description Changes in ionized calcium were studied in axons isolated from living squid by measuring absorbance of the Ca binding dye Arsenazo III using multiwavelength differential absorption spectroscopy. Absorption changes measured in situ were calibrated in vitro with media of ionic composition similar to axoplasm containing CaEGTA buffers. Calcium loads of 50-2,500 μmol/kg axoplasm were induced by microinjection, by stimulation in 112 mM Ca seawater, or by soaking in choline saline with 1-10 mM Ca. Over this range of calcium loading of intact axoplasm, the ionized calcium in the axoplasm rose about 0.6 nM/μM load. Similar loading in axons preteated with carbonyl cyanide 4- trifluoromethoxyphenylhydrazone (FCCP) to inhibit the mitochondrial proton gradient increased ionized calcium by 5-7 percent of the imposed load, i.e. 93-95 percent of the calcium load was buffered by a process insensitive to FCCP. This FCCP- insensitive buffer system was not saturated by the largest calcium loads imposed, indicating a capacity of at least several millimolar. Treatment of previously loaded axons with FCCP or apyrase plus cyanide produced rises in ionized calcium which could be correlated with the extent of the load. Analysis of results indicated that, whereas only 6 percent of the endogenous calcium in fresh axons is stored in the FCCP-sensitive (presumably mitochondrial) buffer system, about 30 percent of an imposed exogenous load in the range of 50-2,500 μM is taken up by this system.
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spelling pubmed-22284652008-04-23 Intracellular calcium buffering capacity in isolated squid axons Brinley, FJ Tiffert, T Scarpa, A Mullins, LJ J Gen Physiol Articles Changes in ionized calcium were studied in axons isolated from living squid by measuring absorbance of the Ca binding dye Arsenazo III using multiwavelength differential absorption spectroscopy. Absorption changes measured in situ were calibrated in vitro with media of ionic composition similar to axoplasm containing CaEGTA buffers. Calcium loads of 50-2,500 μmol/kg axoplasm were induced by microinjection, by stimulation in 112 mM Ca seawater, or by soaking in choline saline with 1-10 mM Ca. Over this range of calcium loading of intact axoplasm, the ionized calcium in the axoplasm rose about 0.6 nM/μM load. Similar loading in axons preteated with carbonyl cyanide 4- trifluoromethoxyphenylhydrazone (FCCP) to inhibit the mitochondrial proton gradient increased ionized calcium by 5-7 percent of the imposed load, i.e. 93-95 percent of the calcium load was buffered by a process insensitive to FCCP. This FCCP- insensitive buffer system was not saturated by the largest calcium loads imposed, indicating a capacity of at least several millimolar. Treatment of previously loaded axons with FCCP or apyrase plus cyanide produced rises in ionized calcium which could be correlated with the extent of the load. Analysis of results indicated that, whereas only 6 percent of the endogenous calcium in fresh axons is stored in the FCCP-sensitive (presumably mitochondrial) buffer system, about 30 percent of an imposed exogenous load in the range of 50-2,500 μM is taken up by this system. The Rockefeller University Press 1977-09-01 /pmc/articles/PMC2228465/ /pubmed/894260 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
Brinley, FJ
Tiffert, T
Scarpa, A
Mullins, LJ
Intracellular calcium buffering capacity in isolated squid axons
title Intracellular calcium buffering capacity in isolated squid axons
title_full Intracellular calcium buffering capacity in isolated squid axons
title_fullStr Intracellular calcium buffering capacity in isolated squid axons
title_full_unstemmed Intracellular calcium buffering capacity in isolated squid axons
title_short Intracellular calcium buffering capacity in isolated squid axons
title_sort intracellular calcium buffering capacity in isolated squid axons
topic Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2228465/
https://www.ncbi.nlm.nih.gov/pubmed/894260
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