GLUCOCORTICOIDS MAY ALTER ANTIOXIDANT ENZYME CAPACITY IN THE BRAIN - BASE-LINE STUDIES

Glucocorticoids (GCs), the adrenal steroids secreted during stress, ha ve been shown to increase the vulnerability of hippocampal neurons to metabolic insults, potentially by altering the neuronal defense capaci ty against oxidative damage. These experiments assessed the effect of long term in vivo GC supplementation on basal activity of the antioxid ant enzymes copper/zinc superoxide dismutase (Cu/Zn SOD), manganese su peroxide dismutase (Mn SOD), catalase, and glutathione peroxidase (GSP x). Kinetic enzyme studies were done using brain tissue from the hippo campus, cortex, cerebellum, and also from Liver as a peripheral contro l. Cu/Zn SOD activity was significantly lower in all brain regions of GC-treated rats, but higher in the liver. Mn SOD activity was unaffect ed by treatment. Catalase in the brain appeared largely unaffected by GC treatment, although liver catalase was significantly decreased. GSP x activity was significantly decreased by GCs at high peroxide levels in all tissues. These results indicate that the presence of GCs may lo wer the antioxidant capacity of tissues in a region-specific manner, a nd that the deficit may not appear until the tissue is challenged with supranormal levels of oxidative products las seen with GSPx). (C) 199 8 Elsevier Science B.V.