Necessary amino acids and vitamins for the growth of human diploid fibroblasts.

Only 2 amino acids and one vitamin were found to be essential for the growth of human embryonic diploid lung fibroblasts when 10% undialysed calf serum was used as a medium supplement. These amino acids were either glutamine + cysteine or serine + homocysteine. Replacing cysteine or homocysteine with cystine or homocystine, respectively, reduced growth. The growth rate in the glutamine + cysteine medium was slightly less than that in Eagle's medium, but the in vitro life time was similar. Folic acid was the only vitamin needed to support cell growth in vitro. The addition of other vitamins had no stimulatory effect with the possible exception of nicotinamide. When other amino acids were added to glutamine + cysteine none showed stimulatory effects but tryptophan was either toxic or inhibitory for the 3 human diploid strains examined. Serine was inhibitory for WI-38 but not for MRC5 cells. Subtle nutritional differences appear to exist between fibroblasts of the same type obtained from different embryos.