Blocking NMDA receptors prevents the oxidative stress induced by acute ammonia intoxication

Acute ammonia intoxication diminishes the activities of antioxidant enzymes and increases superoxide formation in brain. These effects could play a role in the mechanism of ammonia toxicity. It has been shown that ammonia toxicity is mediated by activation of NMDA receptors. The aim of this work was to assess whether ammonia-induced changes in antioxidant enzymes and in superoxide formation are mediated by activation of NMDA receptors. It is shown that MK-801, an antagonist of NMDA receptors prevents ammonia-induced changes in superoxide dismutase, glutathione peroxidase and catalase. Ammonia intoxication also induces a depletion of glutathione and an increase in lipid peroxidation. Both effects, as well as ammonia-induced increase in superoxide formation are prevented by MK-801. These results indicate that ammonia-induced oxidative stress in brain is mediated by excessive activation of NMDA receptors and support the idea that oxidative stress can play a role in the mechanism of ammonia toxicity.