The effects of G418 on the growth and metabolism of recombinant mammalian cell lines

It is widely reported that the growth of recombinant bacteria and yeast is adversely affected by increased metabolic load caused by the maintenance of plasmid copy number and recombinant protein expression. Reports suggest th at recombinant mammalian systems are similarly affected by increased metabo lic load. However, in comparison to bacterial systems relatively little inf ormation exists. It was the aim of this study to test the effects of recomb inant gene expression on the growth and metabolism of two industrially impo rtant cell lines. A BHK and CHO cell line were stably transfected with the human gastric inhibitory peptide (h-GIP) and glucagon receptor respectively . Selection was by way of the neomycin resistance (neo(r)) gene using G418. The growth and metabolism of both cell lines was affected by the presence of G418 in a manner indicative of increased metabolic load and which appear ed to be caused by over-expression of the neomycin resistance protein. The two cell lines differed in their metabolic response to G418, which suggeste d that some cell lines or clones may be better able to tolerate a metabolic load than others. Growth under increased metabolic load was affected by me dium composition with serum, insulin and glutamine concentration as influen cing factors. Implications for the use of G418 are discussed.