Intracellular free magnesium in frog skeletal muscle studied with a new type of magnesium-selective microelectrode: interactions between magnesium and sodium in the regulation of [Mg]i
✍ Scribed by L. A. Blatter
- Publisher
- Springer
- Year
- 1990
- Tongue
- English
- Weight
- 986 KB
- Volume
- 416
- Category
- Article
- ISSN
- 0031-6768
No coin nor oath required. For personal study only.
✦ Synopsis
The application of a new type of intracellular magnesium-selective microelectrode based on the neutral carrier ETH5214 to measure intracellular free magnesium ([Mg]i) in frog skeletal muscle fibers is reported. At room temperature (18-20~ the average values for [Mg]i was 0.93 mmol/1 (pMg~ = 3.03 • 0.42, SD; n = 38 experiments). The regulation of [Mg]i was studied by measuring [Mg]~ and [Na]i with ion-selective microelectrodes during alterations of the membrane potential and the transmembrane sodium and magnesium gradients. Depolarization by increasing external [K] from 2.5 retool/1 to 12.5 retool/1 did not significantly influence [Mg]i. Increasing extracellular [Mg] from I retool/1 to 10 and 20 mmol/1 caused a concentration-dependent rise in [Mg]i and a decrease in [Na]i, whereas removal of external magnesium did not affect [Mg]i. Removal of external [Na] caused an increase in [Mg]i and a decrease of [Na]i. The results show that [Mg]i in frog skeletal muscle is not in thermodynamic equilibrium and suggest that a Na/Mg exchange mechanism may be involved in maintaining low levels of [Mg]i.