MANGANESE AND EPILEPSY - BRAIN GLUTAMINE-SYNTHETASE AND LIVER ARGINASE ACTIVITIES IN GENETICALLY EPILEPSY-PRONE AND CHRONICALLY SEIZURED RATS

Low blood manganese (Mn2+) concentration is associated with epilepsy i n humans and rats. The low Mn2+ concentration is attributed by some in vestigators to the seizure activity associated with the epilepsy, wher eas others propose that the low Mn2+ concentration may be secondary to genetic mechanisms underlying the epilepsy. To begin to differentiate between these possibilities, Mn2+-binding enzymes of liver and brain (i.e., arginase and glutamine synthetase, respectively) were assayed i n rats exposed to chronically induced seizures and in genetically epil epsy-prone rats (GEPRs). Chronic seizures caused a decrease in whole b lood Mn2+ levels but did not affect brain Mn2+ concentrations. Arginas e activity was increased in livers of rats with chronic seizure as com pared with controls, but this difference was eliminated when Mn2+ was added to the assay. Brain glutamine synthetase activity was unaffected by chronic seizures, but the activity of this enzyme was significantl y lower in GEPR brain than in control brain. Liver arginase activity t ended to be lower in GEPRs, although the difference was not statistica lly significant. These data indicate that seizures affect liver argina se activity through changes in liver Mn2+ concentration, but GEPRs sho w abnormalities in Mn2+-dependent enzymes apparently independent of se izure activity.