Biochemical and Genetical Studies on Variants of the Mouse Strain L Cells in Cell Culture

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Abstract
Effects of various chemical and physical agents (mytomycin C, 8-azaguanine,, and UV-irradiation) on the cell multiplication and DNA, RNA and protein syntheses of original mouse fibroblastic strain L cells in vitro were studied. The variant cells resistant to these agents were isolated from the original L cells and some detailed properties of these variants were described. Mytomycin C-resistant cells, which were obtained by several successive treatments of mytomycin C in gradual higher levels, showed smaller size in appearance than the original L cells and contained less amounts of proteins, although amounts of DNA and RNA contained in mytomycin C-resistant cells were not different from those in original L cells. Eight-azaguanine-resistant cells showed no marked difference in the cell morphology, cell-multiplication rate and contents of protein, DNA and RNA, from those in the original L cells. Properties of UV-resistant cells were almost comparable with those of the mytomycin C-resistant cells. Cross-resistance was found between mytomycin C- and UV-resistant cells, whereas it was not found between mytomycin C- and 8-azaguanine-resistant cells, and between UV- and 8-azaguanine-resistant cells. Effects of mytomycin C seem to have something common to those of UV-irradiation, which differ from those of 8-azaguaniner It was emphasized that the multiplication of mytomycin C-resistant cells and of UV-resistant cells was accelerated by filterable substances produced from L cells of 8-azaguanine-resistant cells, whereas the multiplication of L cells and 8-azaguanine-resistant cells was not affected by filterable substances from cells of any variants.