Magnesium in cardiac energy metabolism*

Effects of metabolic blockade on intracellular calcium concentration in isolated ferret ventricular muscle.

“…1) The level of [Mg 2+ ]; in heart muscle under normal conditions remains subject to considerable uncertainty. 27 In our earlier work, we used the value of 3 mM measured by Hess et al, 28 but it now appears that correction for the influence of sodium and potassium on the magnesium-sensitive electrode was incorrect in that study, and more recent work suggests values between 0.5 and 2.0 mM. 2729 In the present study, we have therefore taken [ will be overestimated to some extent during these oscillations.…”

Regulation of dynamic behavior of cardiac ryanodine receptor by Mg2+ under simulated physiological conditions

“…The cardiac RyR is modulated by various endogenous modulators, among which perhaps the most important are Mg 2ϩ and ATP (10,33) and luminal Ca 2ϩ (7,18,49). The cytoplasm of resting cardiac muscle contains ϳ3-5 mM total ATP and 0.5-1.2 mM free Mg 2ϩ (2,16,21,37,38). Although the ATP and Mg 2ϩ concentrations are thought not to change rapidly during EC coupling (2), under ischemic conditions, Mg 2ϩ concentration is known to become as high as 2-4 mM, whereas ATP concentration falls nearly to zero (22,37,38 (18,25,27,56).…”

Captopril protects against myocardial injury induced by magnesium deficiency.

“…26 Alterations to the mitochondrial enzyme activities may cause an uncoupling of oxidative phosphorylation, while the MgATP 2+ complex is a substrate for numerous enzymatic reactions. 23 It has also been reported that in magnesium-deficient rats, blood glutathione levels are low, indicating a reduction in GSH biosynthesis. 27 Recently, evidence has been reported of increased membrane fluidity during magnesium deficiency in erythrocytes.…”

“…The free intracellular magnesium concentration is low and varies with time and subcellular structure. 23 In the heart, the magnesium levels are relatively high, with the ventricular content greater than that in the atria. 22 - 24 However, the myocardium is still highly vulnerable to magnesium deficiency, leading to cell degeneration, fibrosis, necrosis, and calcification.…”