Effects of magnesium on the tone of isolated human coronary arteries. Comparison with diltiazem and nitroglycerin.

Abstract

To study the effects of magnesium (Mg2+) on human coronary arteries and to compare those effects with those of diltiazem and nitroglycerin, we measured the tension of ring segments from isolated human coronary arteries obtained at autopsy within 5 hours after death. Precontracted segments with 3 x 10(-6) M prostaglandin F2 alpha were studied after adding cumulative concentrations of these agents (1.0-8.0 mM, 10(-9)-10(-5) M, and 10(-10)-10(-6) M, respectively). Mg2+ significantly inhibited the tonic contraction compared with the time-matched controls at 1.0 and 2.0 mM (48.7 +/- 5.6% vs. 88.6 +/- 2.2%, p less than 0.01, 36.2 +/- 6.1% vs. 78.9 +/- 3.0%, p less than 0.01, respectively). 1.0 and 2.0 mM Mg2+ did not suppress, but actually increased, the amplitude of periodic contraction, but 8.0 mM Mg2+ reduced the amplitude compared with the controls (6.6 +/- 5.2% vs. 73.3 +/- 10.7%, p less than 0.01). Diltiazem at a concentration of 10(-5) M moderately inhibited the tonic contraction, and reduced the amplitude of periodic contraction almost completely. Nitroglycerin reduced the tonic contraction almost completely at a concentration of 10(-6) M but did not reduce the amplitude of periodic contraction at any concentration. We conclude that 1.0 and 2.0 mM Mg2+ inhibits the tonic contraction and that 8.0 mM Mg2+ inhibits the periodic as well as the tonic contraction of isolated human coronary arteries. Diltiazem inhibits the periodic contraction, whereas nitroglycerin suppresses tonic contraction without affecting the periodic contraction.

Effects of Magnesium Supplementation on Blood Pressure

“…Low: ≤3 and high: >3. blood flow, vascular resistance, and capacitance function of vessels, which contributes to the pathoetiology of hypertension. [31][32][33][34] Additionally, Mg has shown its antioxidant benefits in the prevention of hypertension through attenuating the damage of vasculature from oxidative stress and preventing vascular injury. 5,6 Although accumulating evidence from such studies has indicated that low dietary or circulating Mg may be related to the development of hypertension because of its calcium antagonist and endothelial effects, 35 epidemiological evidence for a relationship between Mg intake and hypertension has been controversial.…”

Urinary and plasma magnesium and risk of ischemic heart disease

“…As a consequence, magnesium deficiencies can result in muscle weakness, cramping, and spasm (36). Also, magnesium inhibits tonic contraction of human coronary arteries (37), which could prevent coronary spasm (38) and, in turn, ischemic heart disease. Experimental studies have shown that low magnesium intake causes arrhythmias, such as supraventricular ectopy (39) and atrial fibrillation (40), which ultimately may explain the increased risk of sudden cardiac death associated with low magnesium (41,42).…”

Magnesium Metabolism in Hyperthyroidism.

“…In a recent review [29], none of the various circulating spasmogenic theories could satisfactorily account for coronary vasospasm in hyperthyroidism, and Miyagi et al [30] had shown magnesium to suppress coronary spastic angina. Evidently the potential for decreased magnesium to enhance coronary or cardiac reactivity to vasoactive agonists [31,32] deserves consideration in hyperthyroidism.…”