Objectives: Magnesium sulfate has been recognized as a neuroprotective agent against hypoxia-ischemia, mainly by the protection from the excitotoxicity associated with increased glutamate concentration. However, the mechanism of MgSO4 action is not fully understood and is considerably controversial.

Design and methods: During the 2 first hours of life, the asphyxiated full-term newborns were treated intravenously with one dose of MgSO4 250 mg/kg body weight. At birth, after 6 and 48 h of life the activity of ATP-dependent enzymes in erythrocyte membranes: Mg2+-ATPase, Ca2+-ATPase, protein kinases A and C, were determined. Using monoclonal antibodies, the band 3 and its phosphotyrosine level were also assayed.

Results: The time-dependent decrease of Ca2+-ATPase activity was detected in untreated newborns, whereas MgSO4 prevented this reduction. After 48 h, protein kinases activities differed in MgSO4-treated and untreated groups. Magnesium therapy increased the amount of band 3 and diminished proteolytic degradation of this protein.

Conclusion: Our results demonstrated, for the first time, that magnesium sulfate treatment significantly altered the activities of some important enzymes in erythrocyte membrane from asphyxiated newborns. It also reduced the post-asphyxial damages of membrane compounds. These data may partly explain the molecular mechanisms of MgSO4 action in asphyxiated newborns.