CO2/bicarbonate stimulates growth independently of PH in mouse mammary epithelial cells

Mouse mammary cells of the NMuMG line proliferated faster and formed colonies more efficiently when the air above the cells contained 5% CO2. An increase in colony forming efficiency also occurred if the bicarbonate concentration in the medium was higher (44 versus 13 mM). These growth increases induced by the CO2 or bicarbonate occurred even when the control cultures were maintained at the same pH, and they occurred at every pH tested. Both the growth rate and colony forming efficiency of the NMuMG cells were highest at pH 7.0 to 7.3.