Measurements of intracellular Mg2+ concentration in mouse skeletal muscle fibers with the fluorescent indicator mag-indo-1

L. Csernoch, Jean Claude Bernengo, P. Szentesi, Vincent Jacquemond

Research output: Contribution to journalArticle

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Abstract

Measurements of intracellular free magnesium concentration ([Mg2+](i)) were performed on enzymatically isolated skeletal muscle fibers from mice, using the fluorescent ratiometric indicator mag-indo-1. An original procedure was developed to calibrate the dye response within the fibers: fibers were first permeabilized with saponin in the presence of a given extracellular magnesium concentration and were then embedded in silicone grease. The dye was then pressure microinjected into the saponin-permeabilized silicone- embedded fibers, and fluorescence was measured. The results show that for all tested [Mg2+], the value of the measured fluorescence ratio was higher than that found in aqueous solutions. Furthermore, the apparent binding curve that could be fit to the in vivo ratio data was shifted toward higher [Mg2+] by a factor of ~2. Using the in vivo calibration parameters, the mean resting [Mg2+](i) was found to be 1.53 ± 0.16 mM (n = 7). In an attempt to gain insight into the myoplasmic magnesium buffering capacity, we measured, together with mag-indo-1 fluorescence, the current elicited by the application of carbamylcholine (CCh) to the endplate of isolated fibers, in the presence of a high extracellular magnesium concentration. The results show that, under these conditions, a change in [Mg2+](i) displaying a time course and amplitude qualitatively consistent with the CCh-induced inward current can be measured.

Original languageEnglish
Pages (from-to)957-967
Number of pages11
JournalBiophysical Journal
Volume75
Issue number2
Publication statusPublished - Aug 1998

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Skeletal Muscle Fibers
Magnesium
Fluorescence
Saponins
Carbachol
Silicones
Coloring Agents
Calibration
Pressure
2-(4-(biscarboxymethyl)amino-3-(carboxymethoxy)phenyl)-1H-indole-6-carboxylic acid

ASJC Scopus subject areas

  • Biophysics

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Measurements of intracellular Mg2+ concentration in mouse skeletal muscle fibers with the fluorescent indicator mag-indo-1. / Csernoch, L.; Bernengo, Jean Claude; Szentesi, P.; Jacquemond, Vincent.

In: Biophysical Journal, Vol. 75, No. 2, 08.1998, p. 957-967.

Research output: Contribution to journalArticle

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