Establishment of synthetic growth media for mammalian cell culture.

Eagle showed that a medium containing the 13 amino acids and the seven vitamins found to be essential for the growth of L and HeLa cells, each at the optimum concentration and appropriately supplemented with glucose, does not permit growth unless a small amount of serum was added (Eagle, 1973). Therefore it has been suggested that serum contains macromolecular factors required for multiplication of animal cells. Recent years have witnessed rapid progress in growth-stimulating serum protein factors for vani ous mammalian cell cultures (Paul et al., 1971 ; Salmon et al., 1971; Antoniades et al., 1975). However, little attention has been given to low molecular weight serum ingredients. Recently we found that heavy metals in serum such as zinc and cupric ions are essential for growth and maintenance of mammalian cells. It has long been known that zinc compounds stimulate wound healing in humans (Pories et al., 1967). The mechanism of action of zinc compounds has not been clarified. Recently, however, Loeb and his coworkers (Springgate et al., 1973) showed that zinc ion is an intrinsic metal for E. coli DNA polymerase. Furthermore several investigators have shown that inhibition of DNA synthesis by ethylene diamine tetraacetate (EDTA) in various mammalian cell cultures is prevented or reversed by addition of zinc ions to the culture media (Lieberman and Ove, 1962; Alford, 1970; Rubin, 1972). These observations may also suggest that zinc ions are essential element for mammalian DNA polymerase. Springgate et al. determined that one zinc atom per enzyme molecule of E. coli DNA polymerase is sufficient for catalytic activity of the enzyme (Springgate et al., 1978). Moreover, zinc ions play a similar role in reverse transcriptase (Auld et al., 1974) and DNA dependent RNA polymerase (Scrutton et al., 1971). Since these key enzymes are essential for growth, viability and various biological functions of cells, zinc ions must be indispensable for growth and viability