Density‐dependent effects of oxygen on the growth of mammalian fibroblasts in culture

Various concentrations of oxygen were used to determine the optimum culture medium P   O   2for survival and proliferation of attached human and mouse fibroblasts grown from different inoculum sizes. When T−15 flasks were seeded with ⪕ 2 × 10 4 cells (⪕ 1.3 × 10 3 cells/cm 2 ), the highest plating efficiencies and cell yields were obtained with a culture medium P   O   2of 40—60 mm Hg. At higher inoculum sizes (10 5 cells per T‐15) used routinely for mass cultures, no difference in cell yield or glycolytic activity was observed between cultures gassed with atmospheric, i.e., 18% O 2 (growth medium P   O   2≅ 125—135 mm Hg) and those gassed with 1% O 2 (growth medium P   O   2≅ 40—60 mm Hg). The enhanced clonal growth observed at the latter P   O   2results from an increased proliferation rate rather than more efficient attachment and survival of inoculated cells. Glucose uptake and lactic acid accumulation were increased in sparse cultures sparged with 1% O 2 . A slight extension of lifespan was observed in WI−38 cells serially subcultured with a gas phase of 1% O 2 .