Growth of human diploid fibroblasts in media with different amino acid composition.

Human embryonic diploid lung fibroblasts were capable of growing in a medium consisting of Eagle's MEM vitamins plus 0 1 /tg/ml biotin, Earle's salt solution, 4 mM glutamine, 0 4 raM cystine, 0-5 mM tyrosine, 10 % undialysed calf serum and 1 mM pyruvate. The growth rate and percent cell attachment in this medium was slightly less than in Eagle's MEM but the longevity was about the same. Addition of 0-5-1 -o mM histidine stimulated growth but addition of 0 2 mM phenylalanine, methionine or valine decreased longevity markedly. Maintaining a constant pH of about 7-5-7-6 with 20 mM of the organic buffers HEPES, TES or TRICINE yielded a growth rate equal to or better than that of cells growing in unbuffered medium. Some buffers gave good growth initially but eventually the longevity decreased (2omMBIS-TRIS, 2omMBICINE, iomM TRIS). In almost all cases the initial exposure to the buffers yielded the best growth results.