OBSERVATIONS ON THE INFLUENCE OF GLUTAMINE, ASPARAGINE AND PEPTONE ONGROWTH AND T-PA PRODUCTION OF CHINESE-HAMSTER OVARY (CHO) CELLS

When a transfected CHO cell, that produces tissue-type Plasminogen Act ivator, t-PA, was transferred from a medium based on 5% Fetal Calf Ser um, FCS, to a medium based on 0.8% casein peptone with variable glutam ine and asparagine content, it was observed, that the growth of the ce lls changed from anchorage dependant to suspension culture giving more reproducible cultivations. In the FCS culture t-PA was unstable, obse rved as a decline in t-PA concentration after 250 h. This decline in t -PA concentration was not observed in the serum free culture, although there was a decline in productivity after 200 h. This change in produ ction profile may be attributed to either no proteolytic attack from s erum or by scavenging of proteolytic activities produced by the cells from the peptone peptides. Increasing amounts of glutamine/asparagine gave higher production of t-PA in synchrony with an increasing product ion of ammonia/ammonium ions. Ammonia inhibition does not seem to be a key factor for this cell line as seen with many others.