[Lethal effect of bleomycin on Burkitt lymphoma cells at stationary phase]

Effects of bleomycin on cultured Burkitt lymphoma cells (P3HR-1) at the stationary phase were studied. They showed a marked less sensitivity to bleomycin than the cells at the exponential phase. The cell kinetic analysis revealed that the stationary phase was occupied by G1 cells, which were different from exponential G1 cells at various points of metabolic and nutritive state except for DNA content. Then, by synchronizing the exponential cells with hydroxyurea, the response of G1 cells to bleomycin was obtained. As a result, their sensitivity to the drug was found to almost coincide with that of the stationary cells. Therefore, the less sensitivity of the stationary cells to bleomycin was due to the total occupation of the stationary phase by G1 cells showing originally resistance to bleomycin.