Environmental factors for the growth of animal cells

Summary Although cells can grow throughout a wide range of osmotic pressures, any additional salt beyond that required to meet the minimal level exerts an adverse effect, as evidenced by delay in onset of logarithmic growth, slower growth rate, decreased maximal population, and accelerated death. The toxicity of K⁺ is directly related to the osmotic pressure of the culture. Cells appear to ingest most of the nutrients from the medium within the 1st day after being inoculated into it and do not remove significant amounts of nutrients for the next 7 to 8 days of active growth. Dissolved oxygen and medium oxidation-reduction potential (ORP) do not always vary identically and, of the two parameters, ORP is the more critical. If the ORP of the culture is not held constant during growth, enzymatic activity fluctuates during the culture growth cycle. However, if the ORP is held constant, then enzymatic activity and isoenzyme distribution patterns remain constant during the growth cycle. For L cells, the optimum ORP is 100 mv. The ORP of the medium controls the rate and extent of growth of cells. If the ORP is lowered, cells can be inoculated into media and held at 37°C for at least 5 days with no detrimental effect; then, when the ORP is raised, the cells grow as well as if they had just been inoculated into fresh media. By controlling the osmotic pressure, media composition, and environmental parameters, high yields of cells and virus may be consistently obtained. Presented at the Twenty-fifth Annual Meeting of the Tissue Culture Association in the Paul F. Kruse, Jr. Memorial Symposium on Steady-State Culture of Cells.