Objective: This study demonstrated that magnesium (Mg) reduces free radicals after a brief coronary occlusion-reperfusion sequence.
Background: Magnesium has been shown to reduce infarct size in patients with acute myocardial infarction. We hypothesized that this action of Mg occurs through its action on free radicals.
Methods: Eighteen mongrel dogs were studied (nine control, nine receiving Mg). Catheters were placed into the coronary sinus for continuous blood withdrawal. A Varian E-4 electron paramagnetic resonance spectrometer was used to monitor the ascorbate free radical (AFR) signal in the coronary sinus blood; AFR is a measure of total oxidative stress. Occlusion of the left anterior descending coronary artery for 20 min was followed by reperfusion. The study animals received 4 g Mg intravenously starting at 15 min of occlusion (5 min before reperfusion) and continuing during reperfusion.
Results: Results are presented as percent change from baseline +/- SEM. Magnesium blunted the peak AFR increase: at 4 min of reperfusion there was a 4.7 +/- 3.3% increase in AFR signal in the dogs receiving Mg versus an 18.2 +/- 3.3% increase in the control animals (p < 0.05). Total radical flux was reduced during reperfusion by 53% in the Mg dogs compared with controls (p < 0.05).
Conclusions: Magnesium attenuates AFR increase after an occlusion-reperfusion sequence. To our knowledge this is the first in vivo real-time demonstration of Mg's impact on free radicals.