Free magnesium in sheep, ferret and frog striated muscle at rest measured with ion‐selective micro‐electrodes

Intracellular free magnesium in frog skeletal muscle fibres measured with ion‐selective micro‐electrodes.

“…Mg2+-selective micro-electrodes show significant interference from K+ and, to a lesser extent, from Na+ at the levels in which both cations are reported to be present inside frog skeletal muscle fibres (Lev & Armstrong, 1975;Lanter et al 1980;Hess et al 1982). Therefore to achieve optimum accuracy in measurements of [Mg2+], it is necessary to calibrate the electrodes properly, in solutions resembling as closely as possible the intracellular monovalent cationic environment of the same cells (or cells of the same experimental muscle) in which [Mg2+]1 is wished to be measured (Gamino & Alvarez-Leefmans, 1984).…”

“…Thus, Baylor et al (1982), using three metallochromic indicator dyes intracellularly injected into single twitch fibres isolated from frog muscle, obtained different estimates of [Mg2+]i, ranging from 02 to 6 mM depending on the dye used. Using Mg2+_selective micro-electrodes containing a sensor based on the neutral ligand ETH-1117 (Lanter et al 1980), Hess et al (1982) reported a mean value for [Mg2+]i of 3-3 mm and Lopez et al (1984) found a mean value of 3 8 mm. The values of [Mg2+]i obtained using Arsenazo I and Mg2+-selective microelectrodes are considerably higher than those theoretically expected taking into consideration the concentrations and affinity constants of myoplasmic components which bind Mg2+ (Maughan, 1983), and those estimated with nuclear magnetic resonance (n.m.r.)…”

“…Direct measurements of [Mg2+]i in vertebrate skeletal muscle had not been possible until recently, with the advent of Mg2+-selective micro-electrodes with sufficient response and selectivity for intracellular measurements (Lanter, Erne, Amman & Simon, 1980;Hess, Metzger & Weingart, 1982;Lopez, Alamo, Caputo, Vergara & Dipolo, 1984) and the use of metallochromic indicator dyes (Brinley, Scarpa & Tiffert, 1977;Baylor, Chandler & Marshall, 1982). However, results reported using Mg2+-selective micro-electrodes and metallochromic dyes are as conflicting as those reported using indirect methods.…”

Intracellular calcium concentration during hypoxia and metabolic inhibition in mammalian ventricular muscle.

“…A potential problem from the point of view of these experiments is that aequorin light emission at a given [Ca2+] (Hess & Weingart, 1981); (ii) PCr and ATP are both initially 5 mm (Gibbs, 1978) and both fall to zero. (iii) The binding constants for Mg2+ are as listed in Curtin & Woledge (1978), adjusted to pH 7-0.…”

The effects of inorganic phosphate and creatine phosphate on force production in skinned muscles from rat ventricle.

“…The standard solution composition in these experiments (solution A, Table 1) was similar to that used previously (Kentish, 1984) except that the major anions were proprionate-and BES-, rather than Cl-, and the [Mg2+] was set to 3 mm, rather than 1 mm, in order to reproduce the myoplasmic [Mg2+] (Hess, Metzger & Weingart, 1982 (Kentish, 1984 effects of Pi and ADP were tested. In this case the standard 10 mM-CP was replaced by ATP (total concentration 15 mM) to prevent the rephosphorylation of ADP to ATP by the creatine kinase activity in the muscles.…”