Low extracellular magnesium induces intracellular free Mg deficits, ischemia, depletion of high-energy phosphates and cardiac failure in intact working rat hearts: a 31P-NMR study.
Hemodynamic and 31P-NMR spectroscopic studies were performed on intact, perfused working rat hearts exposed to low (0.3 mM) extracellular Mg([Mg2+]o). Low [Mg2+]o perfusion resulted in rapid and significant falls in cardiac output, coronary flow, stroke volume, developed pressure and the rate-pressure product. Concomitant with this O2 consumption decreased and lactate production increased. Hearts perfused with 0.3 mM, instead of 1.2 mM, [Mg2+]o exhibited significant reductions in [ATP], [PCr], intracellular free Mg ([Mg2+]i), and pHi; a marked rise in intracellular Pi corresponding to a precipitous fall in the cytosolic phosphorylation potential was seen. Reintroduction of 1.2 mM [Mg2+]o failed to reestablish either normal hemodynamics, or high-energy phosphates and intracellular Pi, suggesting irreversible myocyte injury. These observations are consistent with the tenet that low [Mg2+]o can result in marked reduction in oxygen and substrate delivery to the cardiac myocytes, probably as a result of coronary vasoconstriction.
Department of Physiology, State University of New York, Brooklyn 11203.
B M
BM
Altura
R L
RL
Barbour
T L
TL
Dowd
F
F
Wu
B T
BT
Altura
R K
RK
Gupta
D000818:Animals; D003327:Coronary Disease / Q000209:etiology*; D006439:Hemodynamics; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000032:analysis*; D008275:Magnesium Deficiency / Q000150:complications* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D010477:Perfusion; D010710:Phosphates / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D010710:Phosphates; D008274:Magnesium