KINETIC HETEROGENEITY IN DENSITY-SEPARATED MURINE FIBRO-SARCOMA SUB-POPULATIONS

  • 1 January 1982
    • journal article
    • research article
    • Vol. 42  (12) , 4999-5003
Abstract
Murine fibrosarcoma cells can be separated into subpopulations by centrifugation through 10-35% Renografin density gradients. The heavier cell populations are rich in chronically hypoxic cells. In this study, each subpopulation was characterized for thymidine incorporation, thymidine transport, TTP pool sizes, and TTP specific activities. The heavier cell populations have less accessibility to exogenous thymidine, and they have lower endogenous pools of TTP and synthesize lower levels of DNA than do the lighter cell populations. However, if the cells are removed from the tumors and labeled with [3H]thymidine in vitro, all subpopulations synthesize DNA at similar rates. Two-parameter flow cytometry using acridine orange staining following partial acid denaturation of chromatin identified a small quiescent population in the most dense cell fraction, but the small number of these cells cannot account for the results of the biochemical studies. The hypoxic cells in the fibrosarcoma tumors apparently are noncycling or slowly cycling, are in all phases of the cell cycle, and recover their ability to synthesize DNA when cultured under in vitro conditions.