Magnesium deprivation decreases cellular reduced glutathione and causes oxidative neuronal death in murine cortical cultures.

The vulnerability of cultured cortical neurons to oxidative injury is an inverse function of the extracellular Mg2+ concentration. In order to test the hypothesis that depolarization-enhanced release of reduced glutathione (GSH) contributes to this phenomenon, we assessed the effect of Mg2+ deprivation on cellular and medium glutathione levels. Incubation of mixed neuronal and glial cultures in Mg2+-free medium resulted in a decline in cellular total glutathione (GSx) within 8 h, without change in oxidized glutathione (GSSG); no effect was seen in pure glial cultures. This decrease in cellular GSx was associated with a progressive increase in GSx but not GSSG in the culture medium. Cellular GSH loss was not attenuated by concomitant treatment with antioxidants (ascorbate, Trolox, or deferoxamine), but was prevented by the NMDA receptor antagonist MK-801. Mg2+ deprivation for over 24 h produced neuronal but not glial death, with release of about 40% of neuronal lactate dehydrogenase by 48-60 h. Most of this cytotoxicity was prevented by treatment with either antioxidants or MK-801. These results suggest that Mg2+ deprivation causes release of neuronal reduced glutathione via a mechanism involving excessive NMDA receptor activation. If prolonged, cellular GSH depletion ensues, leading to oxidative neuronal death.