SKELETAL-MUSCLE INTRACELLULAR IONIZED MAGNESIUM MEASURED BY P-31-NMR SPECTROSCOPY ACROSS THE MENSTRUAL-CYCLE

Objective: The hormonal regulation of magnesium (Mg) metabolism is poo rly understood. Preliminary evidence suggests that reproductive hormon es may influence Mg concentrations in various tissues. The purpose of this study was to determine if Mg concentrations in blood and muscle a re affected by the phase of the menstrual cycle. Methods: Magnesium me asures were obtained from 16 women over the course of one complete men strual cycle. The principal outcome measure was intracellular ionized Mg ([Mg++]i) in skeletal muscle as measured by P-31 nuclear magnetic r esonance spectroscopy. Three blood measures (serum, red blood cell, an d mononuclear blood cell) of total Mg ([Mg]) were also obtained. Resul ts: Mean Mg concentrations were stable across the menstrual cycle with no evidence of a menstrual cycle phase effect for any of the measures . Furthermore, skeletal muscle [Mg++]i was not correlated with any blo od measure of [Mg].Conclusion: These results suggest that physiologic fluctuations in reproductive hormones do not influence either blood [M g] or skeletal muscle [Mg++]i in healthy, regularly cycling women.