In the present investigation we have studied the effect of bear`s gall on mammalian cells and demonstrated that COS-7 cells, which were derived Monkey kidney cells, had shown almost same extent of growth with 78 hrs in 10% FCS Dulbecco`s Modified Eagle`s medium with bear`s gall and without bear`s gall. But the hybridoma cells which were fused murine myeloma cells and the rat spleen cells for monoclonal antibody production died almost within 48 hrs. To investigate the effect of biosynthetic mechanism, cDNA were transfected to COS-7 cells, and it was shown that cDNA-transfected COS-7 cell had produced 30-40% less the amount of recombinant protein than the medium without bear`s gall.