THE EFFECT OF THE TREATMENT OF HIGH-DOSE METHYLPREDNISOLONE ON NA-K+()MG+2 ATPASE ACTIVITY AND LIPID-PEROXIDATION AND ULTRASTRUCTURAL FINDINGS FOLLOWING CEREBRAL CONTUSION IN RAT/

BACKGROUND Although use of corticosteroid in the management of head tr auma has caused a great deal of controversy, corticosteroids have long been an adjunct in the management of severe closed head injury. The g lucocorticoid steroid methylprednisolone (MP) has been proven to have significant antioxidant effect when administered in an antioxidant-hig h dose after central nervous system injury. METHODS The sodium-potassi um activated and magnesium dependent adenosine-5'-triphosphatase (Na+- K+/Mg+2 ATPase EC.3.6.1.3.) activity, lipid peroxidation, and early ul trastructural findings were determined during the immediate posttrauma tic period in rats. Mechanical brain injury was produced when a calibr ated weight-drop device is allowed to fall on to the skull's convexity over the right hemisphere, 1 to 2 mm lateral from the midline. In gro up I, rats were used to determine Na+-K+/Mg+2 ATPase activity, the ext ent of lipid peroxidation, by measuring the level of malondialdehyde c ontent and normal ultrastructural findings in two different brain area s (cerebral cortex and brain stem), In group II, physiologic saline wa s administered right after trauma in the same amount as methylpredniso lone. In group III rats, methylprednisolone (30 mg/kg) was administere d intravenously right after trauma. RESULTS Na+-K+/Mg+2 ATPase activit y significantly decreased in the cerebral cortex and in brain stem wit hin 2 hours after trauma (p < 0.05), There was significant difference in malondialdehyde content between groups II and III (p < 0.05). Methy lprednisolone treatment reduced malondialdehyde content and induced th e recovery of Na+-K+/Mg+2 activity. CONCLUSIONS These data suggest tha t inactivation of Na+-K+/Mg+2 ATPase is closely correlated to changes of lipid peroxidation and the alteration of the ultrastructural findin gs in the early phases after head trauma, The glucocorticoid steroid m ethylprednisolone has been proven to have significant effect in inacti vation of Na+-K+/Mg+2 ATPase with significant reduction of malondialde hyde content.