Alteration in cardiomyocyte mechanics by suboptimal levels of extracellular magnesium.
The beneficial effects of magnesium supplementation in pathological situations is well known, but the myocardial response to a nominal decrease in the level of magnesium has received relatively little attention. Hypomagnesemia can occur as chronic or acute manifestation of physiological changes, pathological conditions, or pharmacological interventions. Experimental interest was focused on the mechanical changes in adult rat heart myocytes following variation in extracellular Mg2+. Isolated cells were exposed to different levels of extracellular Mg2+ and the amplitude and rate of contraction were measured as a function of change in cell length using a video-based edge-detection system. Investigations have revealed that variation in the level of Mg2+ within physiological limits leads to mechanical changes. A decrease in the level of extracellular Mg2+ was accompanied by a significant increase in contractile amplitude and decrease in the velocities of contraction and relaxation. The contractile amplitude measured as percentage shortening were 3.08+/-0.19%, 4.62+/-0.19% and 6.9+/-0.40%, respectively, on exposure to 1.8, 0.8, and 0.48 mM Mg, and the corresponding velocities of contraction and relaxation normalized to amplitude were 0.54+/-0.02, 0.40+/-0.03, 0.31+/-0.03 and 0.47+/-0.02, 0.35+/-0.02, 0.24+/-0.02. The variations in contractile parameters associated with the change in the level of Mg were statistically significant (p < 0.01). Variation in the contractile properties associated with change in extracellular Mg2+ may be effected by alteration in Ca2+ transients.
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Division of Cellular and Molecular Cardiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India.
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D000818:Animals; D005110:Extracellular Space / Q000502:physiology*; D006321:Heart / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D008274:Magnesium / Q000502:physiology*; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology*; D009206:Myocardium / Q000166:cytology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012518:Sarcomeres / Q000187:drug effects
D008274:Magnesium