Abstract
The effects of various chemical and physical agents (mitomycin 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 determined.
The variant cells resistant to these agents were isolated from the original L cells and some detailed properties of these variants were described. Mitomycin C-resistant cells (LMit cells), which were obtained by several successive treatments of mitomycin C in gradual higher levels showed smaller size in appearance than the original L cells and contained less amounts of protein, although amounts of DNA and RNA contained in LMit cells were not different from those in original L cells. 8-azaguanine-resistant cells (L8-AZ 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 (LUV cells) were almost comparable with those of LMit cells in every point of view.
The appearance of these resistant cells seems to depend on adaptation to or selection by these respective agents rather than on mutagenic actions of these agents.
The cross-resistant phenomenon was found between LMit cells and LUV cells, whereas it was not found between LMit and L8-AZ and between LUV and L8-AZ. These facts suggest that effects of mitomycin C may have something common to those of UV-irradiation, which differ from those of 8-azaguanine.
It was found that the multiplication of LMit cells and of LUV cells was accelerated by filterable substances produced from L cells or from L8-AZ cells, whereas the multiplication of L cells and of L8-AZ cells was not affected by filterable substances from cells of any variants.
