IMMUNOLOCALIZATION OF GLUTATHIONE-REDUCTASE IN THE MURINE BRAIN

Free radical species arise from the univalent reduction of oxygen. The cytosolic agent H2O2, produced during enzymatic scavenging of the sup eroxide radical (. O-2-) is in turn removed predominantly via the oxid ation of reduced glutathione (GSH) to the oxidized form (GSSG) by glut athione peroxidase. Subsequently GSSG is recycled back to GSH by gluta thione reductase (GSH-red). Little is known about the distribution of this enzyme in the brain. The aim of this study was to determine the d istribution of this enzyme in the brain of different murine species by means of immunocytochemical techniques, although most attention was g iven to the distribution of GSH-red in the forebrain. In most brain ar eas GSH-red positive neurons were detected, but the regional intracell ular staining intensity differed markedly. The pre-piriform and pirifo rm cortices, the pyramidal cell layers of the hippocampus, and the den tate gyrus were heavily stained. The caudate nucleus displayed a progr essive increase in the intracellular staining intensity from the rostr al to the caudolateral parts. Furthermore, in the thalamus, there was a gradual decrease in GSH-red staining from the medial to-the lateral parts. The mesencephalon was poor in immunopositive cells, and in the substantia nigra pars reticulata, almost no labeling was detected. How ever, the substantia nigra pars compacta showed an intense GSH-red imm unoreactivity. The results show a specific localization of glutathione reductase in distinct brain regions, suggesting a variable potency of different brain areas in dealing with the damaging oxidative actions of free radicals. Also, differential GSH-red expression patterns were found in the various murine species. Some species showed a pronounced GSH-red immunoreactivity in glial cells, specifically in regions that lacked neuronal GSH-red immunoreactivity. (C) 1996 Wiley-Liss, Inc.