GLUCOSE-6-PHOSPHATE-DEHYDROGENASE ACTIVITY IS HIGHER IN THE OLFACTORY-BULB THAN IN OTHER BRAIN-AREAS

The activity of antioxidant enzymes was measured in the olfactory bulb (OB) of rat and compared with cortex, hippocampus, striatum and septu m. Glutathione reductase, glutathione peroxidase, catalase and superox ide dismutase were not significantly different in the five brain areas , while glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconat e dehydrogenase activities were four times higher in the OB than in th e other areas. This picture prompted us to explore the reasons of the marked increase of G6PD, since it is the enzyme that regulates the ope ration of the hexose monophosphate shunt. A first approach was to anal yze the G6PD electrophoretic pattern. The analysis revealed that the h igh G6PD activity of the bulb was neither due to new isoenzymes nor to a modification of the equilibrium between the G6PD dimers. We secondl y hypothesized an induction of G6PD activity in the OB by oxidant stre ss. The assay of markers of the oxidant stress, such as thiobarbituric acid reactive substances, oxidized and reduced glutathione, did not c onfirm this hypothesis. A third approach was the cytochemical analysis of cryostat sections of OB. By this method we identified a particular cell type which was very rich in G6PD and located at the border of th e glomerular layer. Thus, we attributed the high G6PD activity of the OB to the consistent presence of periglomerular cells, that probably n eed a high G6PD activity for their regulatory function in the neuroche mical transmission.