EFFECTS OF DISSOLVED-OXYGEN LEVELS AND THE ROLE OF EXTRA-CELLULAR ANDINTRACELLULAR AMINO-ACID-CONCENTRATIONS UPON THE METABOLISM OF MAMMALIAN-CELL LINES DURING BATCH AND CONTINUOUS CULTURES

The effects of dissolved oxygen and the concentration of essential ami no acids upon the metabolism of two mammalian cell lines (rCHO produci ng human active (t-PA) and a mouse-mouse hybridoma) were investigated in batch, chemostat, and perfusion cultures. Intracellular amino acid concentrations were measured for both cell lines during repeated batch cultures and the Ks-values for the essential amino acids were calcula ted using Monod equations via computer simulation. The Ks-values were in the range of 10 mmol L-1 and the pool of most intracellular amino a cids remained constant at about 10-100 fold higher in concentration th an in the medium. No significant differences were observed between the hybridoma and CHO cell. The specific nutrient uptake rates correspond ed with the cell specific growth rate and the effects of reduced disso lved oxygen concentrations only became evident when the DO dropped bel ow 5% of air saturation (critical concentration below 1%). Nevertheles s, a correlation between nutrient concentration and specific oxygen up take was detected.