Intracellular magnesium during myocardial ischemia and reperfusion: possible consequences for postischemic recovery.
Magnesium (Mg2+) is an important regulator of cell energy metabolism, since only MgATP can serve as a substrate for ATP utilizing processes. We used 31P NMR spectroscopy to determine the complexation of ATP with Mg2+ and intracellular free Mg2+ (Mgf) in isolated rat hearts during control perfusion, ischemia and reperfusion. Atomic absorption spectrophotometry was used to determine preischemic and postischemic tissue Mg2+ and release of Mg2+ into the coronary effluent during reperfusion. Mgf increased from 0.60 mmol/l during control perfusion to greater than 6.5 mmol/l after 15 min of ischemia, while we estimated that at that time 6.7 mmol/l Mg2+ had been liberated from ATP. Less than 2% of cellular Mg2+ was released to the effluent during reperfusion after 30 min of ischemia. From spectra obtained during reperfusion the fraction of ATP that was bound to Mg2+ was calculated to be approximately 96% (compared to 94% during control perfusion), indicating that intracellular Mg2+ did not limit the metabolic use of the newly produced ATP. Mgf remained elevated during reperfusion (0.85 mmol/l). We conclude that intracellular Mg2+ deficiency due to leakage of Mg2+ to the extracellular space does not play a role in the poor postischemic recovery in this isolated rat heart model. Nevertheless, high Mg2+ prior to ischemia or during reperfusion may well be protective, due to interactions of Mg2+ with the sarcolemma or intracellular sites, affecting Ca2+,K+ and Na+ distribution and fluxes.
Kirkels
J H
JH
Interuniversity Cardiology Institute of The Netherlands, Utrecht.
van Echteld
C J
CJ
Ruigrok
T J
TJ
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D003327:Coronary Disease / Q000378:metabolism*; D004734:Energy Metabolism; D007424:Intracellular Fluid / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D015425:Myocardial Reperfusion; D009206:Myocardium / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D010725:Phosphocreatine; D000255:Adenosine Triphosphate; D008274:Magnesium