CORRELATION OF ALTERATIONS ON NA-K+MG+2 ATPASE ACTIVITY, LIPID-PEROXIDATION AND ULTRASTRUCTURAL FINDINGS FOLLOWING EXPERIMENTAL SPINAL-CORDINJURY WITH AND WITHOUT INTRAVENOUS METHYLPREDNISOLONE TREATMENT()

The sodium-potassium activated and magnesium dependent adenosine-5'-tr iphosphatase (Na+-K+/Mg+2 AT- Pase EC 3.6.1.3.) activity and lipid per oxidation and early ultrastructural findings are determined in rat spi nal cord at the early stage of trauma produced by a surgical clip on t he thoracal 2-7 segments. The effect of treatment with intravenous met hylprednisolone (MP) was evaluated the basis of these biochemical alte rations and ultrastructural findings in the same model. The specific a ctivity of the membrane bound enzyme Na+-K+/Mg+2 ATPase was promptly r educed in as early as ten minutes following spinal cord injury and rem ained at a level lower than the levels in the control group and in the sham-operated group. Methylprednisolone treatment immediately after t he trauma attenuated the inactivation of Na+-K+/Mg+2 ATPase. On the ot her hand, there was significant difference in lipid peroxide content b etween the sham-operated and the injured animals. Methylprednisolone t reatment reduced thiobarbituric acid reactive substance (TEARS) conten t in Group IV. We determined a positive relationship among membrane-bo und enzyme Na+K+/Mg+2 ATPase activity, malondialdehyde (MDA) content a nd early ultrastructural changes in the traumatized and treated groups . These data provide evidence for a beneficial effect of methylprednis olone on the activation of Na+-K+/Mg+2 ATPase and lipid peroxidation a nd early ultrastructural changes in spinal cord injured rats. The poss ible mechanism of methylprednisolone effects on the membrane function and lipid peroxidation, and the correlation of biochemical changes wit h ultrastructural findings are briefly discussed.