Fig. 5. Pre-treatment of RTG-2 and CHSE-214 cells with the antioxidant N-propylgallate (nPG; 20 µM) for 30 minutes increases the amount of HIF-1 protein after CoCl₂ (200 µM) treatment. Cells were first treated in the presence or absence of nPG and then with CoCl₂ (2 hours) under normal oxygen conditions (21% O₂). Cobalt treatment in the absence of nPG caused an increase in the level of HIF-1 protein. The level of HIF-1 protein was further increased in the presence of nPG. Furthermore, the HIF-1 protein band was broadened in the presence of nPG, a finding compatible with redox-sensitive phosphorylation of the protein. The HIF-1 protein was detected using immunoprecipitation techniques with trout-specific HIF-1 antibody.