[Proliferation of cultured cells with genetically induced resistance to ethidium bromide on synthetic nutrient media...

Lebr 625 and Lebr 350 cells, resistant to ethidium bromide in concentrations 25 and 50 mkg/ml, are able to grow continuously in serum- and protein-free media. Under the same conditions the parental L929 cells are not able to. Two cell lines (625 sf and 350 sf) were established capable of growing in serum- and protein free media. It is found that ethidium bromide is toxic for resistant cells grown the in serum-free medium. The addition of serum lowers the toxic action of ethidium bromide. A continuous growth of resistant cells in serum-free medium (under nonselective conditions) leads to a decreased level of resistance, which may nevertheless persist for a long period of cultivation (over 2.5 years).