AN ATTEMPT TO ADD BIOLOGICAL FUNCTIONS BY GENETIC-ENGINEERING IN ORDER TO PRODUCE HIGH-PERFORMANCE BIOREACTOR CELLS FOR HYBRID ARTIFICIAL LIVER - TRANSFECTION OF GLUTAMINE-SYNTHETASE INTO CHINESE-HAMSTER OVARY(CHO) CELL

In the course of immortalization, hepatocyte cell lines lose their ori ginal differentiated functions, such as ammonia removal and urea forma tion, drug metabolism, serum protein synthesis, etc, (Enosawa et al., Cell Transplant, 5:S39-S40; 1996), With the aim of adding lost or defi cient functions and producing cell lines for the bioreactor of a hybri d artificial liver, rat glutamine synthetase (GS) was transfected into Chinese hamster ovary (CHO) cells, because it is able to lower the am monia level, The GS gene-inserted pSV2 plasmid was transfected into th e CHO-K1 line by electroporation. Transfected CHO (GS-CHO) cells were cultured in a glutamine-free medium containing ammonia, glutamic acid, and the GS inhibitor methionine sulfoximine (MSX), The MSX concentrat ion was increased stepwise from 25 mu mol/L to 1600 mu mol/L to amplif y the GS gene, In several GS-CHO sublines resistant to 300-1600 mu mol /L of MSX, the specific activities of GS were increased from 0.2 x 10( -4) to 1.7-2.9 x 10(-4) unit/10(6) cells, When the amplified GS-CHO ce lls were cultured in the ammonia-containing medium, a slow but steady decrease of the ammonia level was observed when the level was high. Fi nally, the prospect of genetically modulated cells for bioreactors in the hybrid artificial liver is discussed. (C) 1997 Elsevier Science In c.