CYSTEINE-INDUCED ENHANCEMENT OF LIPID-PEROXIDATION IN SUBSTANTIA-NIGRA - COMPARATIVE EFFECT WITH EXOGENOUS ADMINISTRATION OF REDUCED GLUTATHIONE

It is generally accepted that reactive oxygen species have a major rol e in the mediation of cell damage and that free sulphydryl (SH) groups are vital in cellular defence against endogenous or exogenous oxidant s. Modification of cellular oxidant/antioxidant balance has been invol ved in the neuropathogenesis of several diseases, e.g., stroke, Parkin son's disease, Alzehimer's disease and physiological ageing. An increa singly important area of antioxidant defence is based on sulphydryl ch emistry, owing to the role of SH groups in the function of macromolecu lar structures such as enzymes and cellular membranes. Thiols, however , may themselves generate deleterious free radicals, and thionyl radic als, which have been demonstrated to originate in biological systems t hrough enzymatic reactions of different peroxidases, by reacting with molecular oxygen or hydrogen peroxide are able to promote reactions of oxidatives stress. In the present study we provide experimental evide nce suggesting a selective effect of cysteine in promoting reactions o f oxidative stress in the brain areas of substantia nigra and septum, but not in other areas. In contrast, exogenous administration of reduc ed glutathione led to a significant decrease of lipoperoxidation in th e brain areas of cortex and hippocampus, associated to selective chang es in the endogenous pool of thiols.