抄録
The effects of Na-butyrate on the physiological behaviour and on the specific productivity of recombinant tissue plasminogen activator (t-PA) Chinese Hamster Ovary (CHO) cells were characterized. Batch cultures were performed in a 3.5-L bioreactor. Na-butyrate was added either at the mid-exponential growth phase (48h) or at the end of the exponential growth phase (74h). The cultures with Na-butyrate showed higher net specific productivity of t-PA and lower final cell density and viability. Maximum specific productivity of t-PA for all cultures coincided with the early plateau phase (84h). The cell's specific oxygen uptake rate (qO_2) increased after the Na-butyrate addition and remained higher than that of the controlled culture. Triphosphate nucleotides, ADP, AMP and UDP-sugars all increased after 84h in the cultures with Na-butyrate, showing different behaviours when Na-butyrate was added at 48h or 74h. Na-butyrate did not affect the cell's adenylate energy charge until the cell's viability started to decrease (156-168h). The controlled culture and the culture with Na-butyrate addition, showed at 74h, similar time trends as for purine and nucleotide ratios ((ATP+GTP)/(UTP+CTP) and UTP/ATP) with clear shifts in behaviour at 84h and 168h. However, the addition of Na-butyrate at 48h resulted in damped variations of purine and nucleotide ratios in comparison to both the control culture and the culture with Na-butyrate addition at 74h.
