α-Keto Acids in Tissue Culture. II. Studies on the Used Medium

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Abstract
Eleven mammalian cell strains, 9 from the tissues of the C3H/HeN mouse and 2 of human origin, were examined for the quantity of keto acids that during growth they contributed to the used medium, in excess of that supplied by the medium. At 72 hours after fluid renewal, the cells had added the indicated quantities of keto acids as µmoles per 100 million cells per 100 ml. of medium: strain 721 of mouse liver epithelial origin, 730; strain 1469 of single cell origin from strain 721, 800; strain 1795 hepatoma rising from strain 1469, 640; sarcoma strain 929L, 430; strain 2071, a strain from 929L adapted to growth in protein-free medium, 500; high sarcoma fibroblast strain 1742, 225; low sarcoma strain 2049, 226; high sarcoma strain 1745, 620; high sarcoma strain 2050, 285; human epidermal strain 2198, 425; and human cervical carcinoma strain 1985 (HeLa), 232. The horse serum of the mediums used for all strains except 2071 contained the transaminase activities for the glutamic-oxalacetic and glutamic-pyruvic transaminations. However, incubation of the medium in the absence of cells produced little change in the keto acid content of the medium. The cells of strain 1469 were broken up and their extracts were found to have active transaminating enzyme systems. It would appear that the excess keto acids put into the mediums by growth of the cells reflect the metabolic activity of the cells.