FIG. 5.

Buffering of culture medium increases the growth of wild-type cells, but not null cells, during the late log phase of growth during prolonged culture at hypoxia. The growth rate of wild-type (A) and HIF-1α-null (B) cells cultured in high-glucose DMEM with or without supplementation with 25 mM (final concentration) HEPES buffer (pH 7.4) was compared at hypoxia over time. Buffering the medium had no effect on HIF-1α-null cells (see panel B) but significantly enhanced the late log phase of growth in wild-type cells between 72 and 120 h at hypoxia. Symbols: ⧫, +/+; ▴, +/+ (HEPES); ■, −/−; ✠, −/− (HEPES).