These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Intracellular free magnesium in frog skeletal muscle fibres measured with ion-selective micro-electrodes.
    Author: Alvarez-Leefmans FJ, Gamiño SM, Giraldez F, González-Serratos H.
    Journal: J Physiol; 1986 Sep; 378():461-83. PubMed ID: 2432253.
    Abstract:
    Intracellular free Mg2+ concentration [( Mg2+]i) was measured in frog skeletal muscle fibres, using Mg2+-selective micro-electrodes based on the neutral ligand ETH-1117. In calibration solutions the electrodes showed significant interference from K+, and to a lesser extent from Na+, at concentrations found intracellularly. Therefore, in order to calibrate the electrodes properly, it was necessary first to obtain an accurate value for intracellular free Na+ and K+ concentrations ([Na+]i and [K+]i), using the appropriate liquid ion exchanger micro-electrodes. In fibres from muscles maintained in Ringer solution, the mean value for [Na+]i was 6.2 +/- 0.4 mM (S.E. of mean; n = 20 fibres in five muscles), while [K+]i was 104 +/- 1.7 mM (range 83-122 mM; n = 25 fibres in eight muscles). Due to the substantial variability found for [K+]i, not only between fibres from different muscles, but also between fibres belonging to the same muscle, it was necessary to measure [Mg2+]i and [K+]i simultaneously in the same fibre to determine as accurately as possible the degree of K+ interference on Mg2+-selective micro-electrode response. In nineteen fibres from six muscles maintained in Ringer solution, the mean [K+]i was 91.7 +/- 2.7 mM (range 71-110 mM), while the mean [Mg2+]i was 0.80 +/- 0.07 mM (range 0.2-1.2 mM). The mean resting potential was -79.3 +/- 0.4 mV (S.E. of mean). In fifteen fibres from four muscles equilibrated in Ringer solution containing 0.5 mM-Mg2+, the mean [K+]i was 115.5 +/- 0.1 mM (range 97-129 mM) and the mean [Mg2+]i measured simultaneously in the same fibres was 1.69 +/- 0.21 mM (range 0.2-2.7 mM). The mean resting potential was -83 +/- 0.7 mV. The mean [K+]i and [Mg2+]i found in these fibres was significantly higher (P less than 0.0001) than those measured in fibres from muscles maintained in standard Ringer solution (i.e. without external Mg2+). Possible explanations for this finding are discussed. Whether in the presence (0.5 mM) or in the absence of external Mg2+, our values for [Mg2+]i are distinctly lower than those previously reported by others, using the same type of Mg2+-selective micro-electrodes but calibrated simply from assumptions about the actual level of K+ and Na+ interference on Mg2+-selective micro-electrode response.(ABSTRACT TRUNCATED AT 400 WORDS)
    [Abstract] [Full Text] [Related] [New Search]