PEROXIDATION OF BRAIN LIPIDS IN-VITRO - NITRIC-OXIDE VERSUS HYDROXYL RADICALS

The pro-oxidant effects of hydroxyl radical (. OH, ferrous ammonium su lfate/Fe2+) or nitric oxide (NO ., S-nitroso-N-acetylpenicillamine/SNA P) generating compounds were studied in rat brain homogenate preparati ons. Submicromolar concentrations of Fe2+, but not SNAP (up to 100 mu M), increased the formation of fluorescent products of malondialdehyde in cortical homogenates. In fact, iron-catalyzed brain lipid peroxida tion was inhibited by SNAP (100 mu M), but not by light-exposed SNAP o r its degradation product penicillamine (100 mu M). This study provide s relevant evidence to suggest that submicromolar concentrations of Fe 2+ can potentiate lipid peroxidation in disrupted brain tissue. NO . r eleased from SNAP did not stimulate, but rather inhibited brain lipid peroxidation. These results support the hypothesis that NO ., as oppos ed to . OH radicals, is not a pro-oxidant but rather an antioxidant.