Fig. 2. Changes in the activity of antioxidant enzymes catalase (A), SOD (B) and GPx (C) in the lungs of the chicken Gallus gallus during late development and at hatch. Solid lines indicate changes under normoxic conditions and dashed lines indicate changes under hypoxic (17 % O₂) conditions. Values are units mg^–1 protein and are means ± S.E.M. In all cases N=4–6. Pairs of symbols (* and ) within the same experimental group indicate points that are significantly different from one another (P<0.05). indicates points for which there is a significant difference in antioxidant enzyme activity between normoxic and hypoxic conditions.