The Specific Amino Acid Requirements of a Mammalian Cell (Strain L) in Tissue Culture

There have been many attempts to devise chemically defined media which will permit the propagation of mammalian cells in tissue culture, without supplementation by serum, plasma, or tissue extractives.To date, these attempts have not been successful.Although some of these media, notably those recently developed by Morgan, Morton, and Parker (1) and by Healy, Fisher, and Parker (Z), permit the survival of some cell lines for long periods, in our hands none has allowed continuing multiplication on serial subculture.Growth can be obtained on the addition to such media of a small amount of serum, but the medium is then no longer chemically defmed and no longer permits the delimitation of the essential growth requirements of the cell.Recognizing this di&ulty, Fischer (3) had used the expedient of supplementing a defined medium with dialyzed chicken plasma, serum, and embryo extract, in the hope that the essential small molecular weight components of the defined medium could then be identified.On the omission of either cystine, arginine, tryptophan, glutamine, or histidine and proline, there was in fact a decrease in the amount of radial growth from a chick embryo myoblast explant.However, growth was not prevented, and no single component could be rigorously characterized as essential to survival and growth.In the light of the dat,a to be reported here, it is possible (a) that the culture materials used by Fischer were not adequately dialyzed, (b) that the large amount,s of plasma and serum employed (more than 50 per cent by volume) contained compounds which could substitute in part for the amino acids, or (c) that the diameter of radial growth around the explant was not a true measure of cell proliferation.In any event, in the simpler system used here, in which cells were grown on a glass surface, the addition of small amounts of dialyzed horse serum to an otherwise defined medium permitted long term propagation of the adult mouse fibroblast (L strain).In such a limiting medium, the omission of a single essential growth factor now resulted in the early death of the culture, and it proved 839