VITAMIN-E, ASCORBATE, GLUTATHIONE, GLUTATHIONE DISULFIDE, AND ENZYMESOF GLUTATHIONE METABOLISM IN CULTURES OF CHICK ASTROCYTES AND NEURONS- EVIDENCE THAT ASTROCYTES PLAY AN IMPORTANT ROLE IN ANTIOXIDATIVE PROCESSES IN THE BRAIN

GSH, GSSG, vitamin E, and ascorbate were measured in 14-day cultures o f chick astrocytes and neurons and compared with levels in the forebra ins of chick embryos of comparable age. Activities of enzymes involved in GSH metabolism were also measured. These included gamma-glutamylcy steine synthetase, GSH synthetase, gamma-glutamyl cyclotransferase, ga mma-glutamyltranspeptidase, glutathione transferase (GST), GSH peroxid ase, and GSSG reductase. The concentration of lipid-soluble vitamin E in the cultured neurons was found to be comparable with that in the fo rebrain. On the other hand, the concentration of vitamin E in the astr ocytes was significantly greater in the cultured astrocytes than in th e neurons, suggesting that the astrocytes are able to accumulate exoge nous vitamin E more extensively than neurons. The concentrations of ma jor fatty acids were higher in the cell membranes of cultured neurons than those in the astrocytes. Ascorbate was not detected in cultured c ells although the chick forebrains contained appreciable levels of thi s antioxidant. GSH, total glutathione (i.e., GSH and GSSG), and GST ac tivity were much higher in cultured astrocytes than in neurons. gamma- Glutamylcysteine synthetase activity was higher in the cultured astroc ytes than in the cultured neurons. GSH reductase and GSH peroxidase ac tivities were roughly comparable in cultured astrocytes and neurons. T he high levels of GSH and GST in cultured astrocytes appears to reflec t the situation in vivo. The data suggest that astrocytes are resistan t to reactive oxygen species (and potentially toxic xenobiotics) and m ay play a protective role in the brain. Because enzymes of GSH metabol ism are generally well represented in cultured astrocytes and neurons these cells may be ideally suited as probes for manipulating GSH level s in neural tissues in vitro. Cultured astrocytes and neurons should b e amenable to the study of the effects of various metabolic insults on the GSH system. Such studies may provide insights into the design of therapeutic strategies to combat oxidative and xenobiotic stresses.