Importance of timing of magnesium administration: a study on the isolated ischemic-reperfused rat heart.

The present study attempted to explore the antioxidant potential of magnesium (2 and 10 mM) in the postischemic isolated rat heart. Magnesium demonstrated a significant antioxidant effect, as deduced by thiobarbituric acid reactive material and glutathione levels. However, this effect was evident only when magnesium was administered prior to ischemia but not when administered during reperfusion. On the other hand, attenuation of calcium accumulation following reperfusion was noted in both treatment schedules and showed dose dependency when administered during reperfusion. Thus, the results of this study strongly suggests an antioxidant effect of magnesium which is distinct from its calcium antagonising effects and it also stresses the critical role played by the time of administration of magnesium.