Magnesium reduces free radicals in an in vivo coronary occlusion-reperfusion model

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 APR 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.