AN ANALYSIS OF THE EFFECT OF “CONDITIONED MEDIUM” UPON THE CELL CULTURE AT LOW DENSITY

A bstract A favorable effect of “conditioned medium” upon outgrowth of the cell culture with low density in vitro was analysed with the cells of chicken embryos. For preparing “conditioned medium”, cultures with a large number of cells were made with muscle, kidney, lung, liver and skin, while the biological activity of the medium was assayed by using the culture of a small number of the lung secondary cells. A use of “conditioned medium” was found to be necessary for encouraging the outgrowth of the cultured cells below a critical inoculum size. Of the various types of the media tested, the medium conditioned with muscle was most effective. “Conditioned medium” contained at least two different active factors, the first to enhance the plating efficiency of the inoculated cells to the surface of the culture dish, and the second to promote further outgrowth of the plated cells. “Conditioned medium” taken out of the mass culture at its exponentially growing phase had only the second factor, while that taken out of that at its stationary phase contained both factors. An activity of the first factor was not detected, when the mass culture was kept in such condition that the collagen synthesis was inhibited. The factor for enhancing the plating efficiency was eliminated from “conditioned medium” by preincubating the cells, before assaying the effect of the medium.