Fig. 2. Relative mean normalized expression (MNE) of superoxide dismutase (SOD), catalase, phospholipid hydroperoxide glutathione peroxidase (GSH-Px), metallothionein (MT) and cytochrome P450 1A (CYP1A) in liver of Atlantic cod exposed to 46%, 76% and 145% O₂ levels. The box plots show median, 25th and 75th percentiles (box) and error bars the range (highest to lowest values); N=6. Kruskal-Wallis; overall P values are shown in the graphs. 1, significant difference between the hypoxia and normoxia groups; 2, significant difference between the hypoxia and hyperoxia groups.