Improvements in a chemically defined medium for the growth of mouse cells (strain LS) in suspension.

In the medium used in previous work, both growth rate and maximum cell population density were reduced in protein-free medium. This was due to iron limitation. In a medium supplemented with iron, the average minimum population doubling time was reduced from 78 to 37 h and the average maximum cell population density increased from I-6XIO° to 33 x io°/ml. In the improved medium described, sodium pyruvate, a-ketoglutaric acid, methylcellulose and polyvinylpyrrolidone are no longer required although methylcellulose prevents an initial fall in population which occurs in polymer-free medium. The present study indicates that amino acids now limit maximum cell population density. By increasing the concentration of the relevant amino acids we have obtained maximum cell populations in excess of 5 x io cells/ml without medium change. Finally we describe a method for measuring the growth of the LS cell in the denned medium by an opacity method.