FIGURE 1.

Loss of hypoxic response induced by CoCl₂ in RPMI-cultured PC12 cells. A, schematic representation of reporter plasmids. B, medium-dependent induction of reporter activity induced by CoCl₂ in PC12 cells. C, chemical hypoxia-inducible reporter activity recovered by the addition of magnesium, Thr, and His to RPMI. 3Mix indicates a mixture of magnesium, Thr, and His, giving equivalent concentrations to those present in DMEM. D, effect of addition of increasing amounts of magnesium, His, and Thr to RPMI on reporter activity. 1x, 3x, 5x, and 10x indicate addition of amino acids to RPMI whose concentrations are equal to, three times, five times, and 10 times higher than that of DMEM. E, Western blot analysis of HIF-1α protein induced by CoCl₂ in PC12 and Hep3B cells. *, p < 0.05 for indicated comparison. The data shown in the bar graphs are the averages ± S.D. of three independent experiments.