Fig. 1. Hypoxia (1% oxygen for 2 hours) causes an increase in the level of hypoxia-inducible factor 1 (HIF-1) in RTG-2 cells as detected by a polyclonal antibody, produced against the HIF-1 protein of rainbow trout (Soitamo et al., 2001). The hypoxia-induced increase in HIF-1 protein level is reduced by previous treatment of the cells under oxidizing conditions (24-hour culture in the presence of 50 µM BSO). (A) A representative gel showing the intensities of HIF-1 protein bands under normal oxygen conditions (21% oxygen), hypoxia (1% oxygen) and hypoxia after culture for 24 hours in the presence of BSO (1% + BSO). (B) Quantification of HIF-1 protein band intensities in normal oxygen before the experiments (21% oxygen), under hypoxia (1% oxygen) and hypoxia after culture for 24 hours in the presence of BSO (1% + BSO). The intensity of HIF-1 protein band in normal oxygen at the onset of the experiments was taken as 100%. BSO treatment to induce oxidative stress decreased the hypoxia-induced induction of HIF-1 protein significantly (P<0.01, paired t-test, SPSS statistical software). Values represent mean±s.e.m. (n=4).