Analysis of Cell Flow and Cell Loss Following X-Irradiation Using Sequential Investigation of the Total Number of Cells In the Various Parts of the Cell Cycle

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Abstract
The cell flow and cell loss of an in vivo growing Ehrlich ascites tumor were calculated by sequential estimation of changes in the total number of cells in the cell cycle compartments. Normal growth was compared with the grossly disturbed cell flow evident after a 5 Gy [Gray] X-irradiation. The doubling time of normal, exponentially growing cells was 24 h. The generation time was 21 h based on double-isotope labeling studies and the potential doubling time was 21 h. The growth fraction was 1.0 and the cell loss rate .apprx. 0.5%/h. Following irradiation, a transiently increased relative outflow rate from all cell cycle compartments was found at .apprx. 3 and 40 h, and from S phase at 24 h after irradiation. Minimum flow rates from all compartments were found up to 20 h. Cell loss as calculated from the cell flow was compared with non-viable cells determined by Percoll density separation. Increase in cell loss as well as non-viable cells was observed at 24 h after irradiation at the time of release of the irradiation-induced G2 blockage. Up to 50 h, .apprx. 70% of the initial total number of cells were lost. The experiments show the applicability and limitations of cell flow and cell loss calculations by sequential analysis of the total number of cells in the various parts of the cell cycle.