Oxygen, bicarbonate, and acid metabolism determinations in mouse cell microcarrier culture

In the design of bioreactors for mammalian cell culture, metabolic parameters such as oxygen uptake, acid output, and CO, generation are desirable. Knowledge of cellular oxygen uptake rates allows the design of systems which supply adequate oxygen for cell growth and product ex- pression. Knowledge of cellular acid output rates allows the formulation of media with sufficient buffering capac- ities to limit the pH change of cultures and provides a basis for the design of systems with pH control. Knowledge of cellular CO, and carbonate uptake or output allows the de- sign of systems which will supply or remove these species. The methods described in this study involve the use of a glass syringe for the culture of animal cells.’ The physical conditions under which the cells are exposed are similar to those of large scale cultures with respect to nutrient sup- ply, cell concentration, microcarrier concentration, etc. As such, the effects of various experimental conditions ob- tained from these techniques can be used for the design of large-scale processes. The oxygen uptake rate of mammalian cells in culture has been measured by various methods. Fleischaker and Sinskey’ measured the oxygen demand in human diploid foreskin cells in microcarrier culture using an oxygen bal- ance equation. The oxygen uptake rate (OUR) was deter- mined using the transport characteristics of the culture vessel by measuring the oxygen concentration transients. Frame and Hu3 measured the OUR of swine testicular cells in 50 mL flasks with no gas phase using an oxygen elec- trode. Additional methods for measuring the oxygen up- take of animal cells involve the measurement of oxygen tensions in completely filled tissue culture flasks with a polarographic electrode4 as well as measuring the disap- pearance of oxygen in a closed chamber by electron spin resonance techniques.5 Bicarbonate and CO, are important mainly in the control of pH as a result of the following equilibria: HC0