THE UPTAKE OF NA-SELENITE IN RAT-BRAIN - LOCALIZATION OF NEW GLUTATHIONE PEROXIDASES IN THE RAT-BRAIN

Polyunsaturated fatty acids (PUFAs) occur in phospholipids of synapses of central nervous system (CNS). PUFAs may thus determine the fluidit y of synaptosomal membranes and regulate neuronal transmission. If was therefore tempting to suggest an oxidative system in CNS protecting t he membrane function, e.g., glutathione peroxidase (GSH-Px). In order to trace GSH-Px Wistar rats were loaded with 4800 kBq of Se-75 sodium selenite. By means of gradient ultra-centrifugation, particulate fract ions of CNS were isolated and radioactivity as well as selenium depend ent GSH-Px were estimated. The following data were obtained: 1. All fr actions (myelin, synaptic vesicles, synaptosomes, mitochondria, and mi crosomes) contained Se-75. 2. After acetone precipitation of GSH-Px ac tivity, fractionation on Sephadex G-150 revealed in all particulate fr actions at least two peaks of radioactivity with GSH-Px activity. 3. T he two GSH-Px peaks from the Sephadex filtration were freeze dried and applied on a hydrophobic T-gel column and eluted with decreasing mola rity of ammonium sulfate from 1.5 to 0.05M. The first Sephadex peak wi th GSH-Px activity from myelin and the second peak with GSH-Px activit y from synaptic vesicles could now be resolved into two different frac tions of radioactivity on the T-gel. The remaining Sephadex G-150 peak s could only be resolved into one peak of radioactivity. 4. SDS-polyac rylamide gel electrophoresis of the T-gel peaks from all fractions sho wed a protein band with a mobility identical with that of human erythr ocyte GSH-Px. The T-gel elution of myelin, synaptic vesicles and mitoc hondria gave rise to nearly pure CNS GSH-Px activity. The data present ed support the idea that CNS fractions have membrane bound GSH-Px acti vity that may function as protecting enzymes towards oxidative stress in the brain.