Background: Hypoxia is a representative stress environment.When an organisms is subjected to severe hypoxia, many kinds of diseases, such as stroke, will occur.On the other hand, adaptive responses are induced to promote survival under moderate hypoxia.Investigating the characteristics of cell metabolism under different levels of hypoxia will be contribute to clarify the mechanism s of hypoxia adaptation.Methods: The PC12 cells were exposed to 0.3% O2 (severe hypoxia) and 10% O2 (moderate hypoxia) for 24 h.Cell viability was assessed by MTT assay.The levels of T-AOC (total antioxidant capacity) were measured using commercial assay kits according to the manufacturers instructions.The HIF-1α and BNIP3 proteins were determined by Western blot analysis.Results: (1) Cell viability texted by MTT assay shows that the number of PC 1 2 cells is clearly increased after 24 h of moderate hypoxia (P<0.001 vs control), and decreased after 24 h of severe hypoxia (P<0.001 vs control).(2) After 24 h of moderate hypoxia, the level of T-AOC was increased, and after 24 h of severe hypoxia, the level of T-AOC was significantly decreased (P<0.05 vs control).(3) After 24 h of hypoxia (moderate hypoxia and severe hypoxia), the expression of HIF-1 α and BNIP3 increased.Compared with severe hypoxia, we observed increased HIF-1α expression and decreased BNIP3 expression in moderate hypoxia.Conclusions: (1) Treatment of severe hypoxia (0.3% O2) lecreased cell viability and the capacity to cell maintain redox homeostasis, and treatment of moderate hypoxia (10% O2) increased cell viability and the capacity to maintain redox homeostasis.(2)We surmise that HIF-lα and its target gene BNIP3 play a role in the regulation of antioxidant capacity, and affect the level of cell survival under different levels of hypoxia.