We analyzed the effects of S-adenosyl-L-methionine (AdoMet) on tissue oxidative stress in rat brain slices exposed to reoxygenation after oxygen-glucose deprivation. The thiobarbituric acid reactive substances (TBARS), total and oxidized glutathione, and lactate-dehydrogenase efflux (LDH) from tissue to the incubation medium, were measured. Brain slices were incubated without glucose and with N-2, then glucose was added and O-2 was perfused. After the anoxic-reoxygenation period, increase in TEARS, oxidized glutathione and LDH efflux, and decrease in total glutathione levels, were observed. The incubation with AdoMet before the anoxic period reduced TEARS (31-1000 mumol/l), glutathione production was increased (31-1000 mumol/l), LDH efflux decreased 6.41% with 15 mumol/l and 61.5% with 500 mumol/l). In the ex vivo experiments, we administered 50 mg/kg per day p.o., AdoMet for 3 days, then brain slices were collected and the anoxia-reoxygenation experiment was carried out. AdoMet led to the inhibition of brain lipid peroxidation and increased total glutathione production, after 3 h-reoxygenation. The increase of LDH efflux in non-treated rats was reduced by 77%. We conclude that AdoMet exerts citoprotective effects in an experimental model of brain slices reoxygenation after oxygen-glucose deprivation. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.