Objective     To explore the effects of hypoxic preconditioning on hypoxia/reoxygenation of cultured cerebral astrocytes.      Methods     The cerebral astrocytes isolated from neonatal SD rats were divided into three groups: normal control

HP groups (receiving hypoxic preconditioning respectively for 24

48

72

96 h

then hypoxia/reoxygenation) H/R group (receiving no hypoxic preconditioning but hypoxia/reoxygenation). MTT metabolic activity of the astrocytes by MTT reduction assay

their apoptotic ratio by flow cytometry were examined and their ultrastructure were observed under transmission electron microscope. SOD activities and MDA were detected.      Results     Hypoxic preconditioning could improve the tolerance of astrocytes to hypoxia/reoxygenation. MTT metabolic activity of the astrocytes in HP48 and HP72 groups was increased as compared with H/R group. The apoptotic ratio of HP48 group was decreased significantly as compared with H/R group. SOD activity was also increased and MDA was decreased. More cells of normal ultrastructure in HP48 group were observed than in H/R group.      Conclusion     Hypoxic preconditioning can improve astrocytes’ tolerance to hypoxia/reoxygenation by increasing SOD activity to inhibit oxygen free radicals.