Growth inhibition in animal cell culture. The effect of lactate and ammonia.

Eight independent cell lines accumulated ammonia in culture to concentrations between 1.3 and 2.9 mM. The growth inhibition of such concentrations of ammonium chloride when added to culture medium was variable. The cell lines tested could be divided into 3 groups depending on their growth response to 2 mM added NH4Cl. In the first group (293, HDF, Vero, and PQXB1/2) little (less than 14%) or no growth inhibition occurred. In the second group (McCoy and MDCK) a reduction in final cell yield of 50-60% was observed. The third group (HeLa and BHK) was most sensitive to the effects of NH4Cl with growth inhibition (greater than 75%) compared to controls. The growth inhibitory effect of added lactate up to 20 mM was negligible (less than 10%) for 3 cell lines, although one cell line (PQXB1/2) showed greater sensitivity. The interactive effects of ammonia and lactate were determined in a matrix experiment. At lactate (greater than 12 mM) and ammonia (1-4 mM), the growth inhibitory effects of the two components were synergistic. However, at low concentrations of lactate (less than 12 mM) the toxic effect of ammonia was reduced. A proposed mechanism for the sparing effect of lactate on ammonia toxicity is discussed. This may have importance in developing strategies for the optimal growth of ammonia-sensitive cell lines.