CHANGES IN ENDOGENOUS LIPOPEROXIDATION AND ANTIOXIDANT ENZYME STATUS INDUCED BY CYSTEINE IN THE SUBSTANTIA-NIGRA

It is generally accepted that reactive oxygen species have a major rol e in the mediation of cell damage and that free sulfhydryl groups are vital in cellular defence against endogenous or exogenous oxidants. Mo dification of cellular oxidant/antioxidant balance has been involved i n the neuropathogenesis of several diseases, e.g., stroke, Parkinson's disease, Alzheimer's disease and physiological ageing. An increasingl y important area of antioxidant defence is based on sulfhydryl chemist ry, owing to the role of -SH groups in the function of macromolecular structures such as enzymes and cellular membranes. Thiols, however, ma y themselves generate deleterious free radicals. In the present study we provide experimental evidence suggesting a selective effect of cyst eine in promoting reactions of oxidative stress in the brain areas of substantia nigra and septum, but not in other different areas which we re associated with corresponding changes in the activity of antioxidan t enzymes.