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 role in the mediation of cell damage and that free sulfhydryl groups are vital in cellular defence against endogenous or exogenous oxidants. Modification of cellular oxidant/antioxidant balance has been involved in the neuropathogenesis of several diseases, e.g., stroke, Parkinson's disease, Alzheimer's disease and physiological ageing. An increasingly important area of antioxidant defence is based on sulfhydryl chemistry, owing to the role of -SH groups in the function of macromolecular structures such as enzymes and cellular membranes. Thiols, however, may themselves generate deleterious free radicals. In the present study we provide experimental evidence suggesting a selective effect of cysteine in promoting reactions of oxidative stress in the brain areas of substantia nigra and septum, but not in other different areas which were associated with corresponding changes in the activity of antioxidant enzymes.