Preventive effect of several antioxidants after oxidative stress on rat brain homogenates.

Brain homogenate was used as a model system to study antioxidant properties of several natural and synthetic antioxidants under oxidative stress. Oxidative stress was induced by Fe/ascorbate system and lipid peroxidation as well as protein modification were studied. Thiobarbituric acid reactive substances (TBARS) were used as a marker of lipid peroxidation. The preventive effect concerning lipid peroxidation decreased in the order: buthylated hydroxytoluene (BHT) (3.5), stobadine (ST) (35), serotonin (54), trolox (98), U 74389G (160), melatonin (3100), (the numbers in the brackets represent IC50 in micromol/l). Methylprednisolone had no effect, and spin traps interfered with TBARS determination. Concerning creatine kinase (CK) activity as a selected marker of oxidative modification of proteins, the preventive effect of antioxidants (30 micromol/l) decreased in the order: BHT (30), trolox (75), stobadine (ST) (77), alpha-phenyl-N-tert-buthylnitrone (PBN) (87), sodium salt of N-tert-buthyl-C-(phenyl-2-sulfone) nitrone (SPBN) (90), (the numbers in the brackets represent the loss of CK activity in percentages, when 100% was the loss of CK activity in the absence of any antioxidant). The nonglucocorticoid steroid U 74389G, methylprednisolone and serotonin had no preventive effects, while melatonin had antioxidant effect only in a higher concentration (1 mmol/l).