Abstract
Background
Apparently normal rat liver epithelial cells (WB‐F344) have been widely used in studies pertaining to carcinogenesis. Ionizing radiation, a well known carcinogen, is known to perturb cell‐cycle progression in a dose‐dependent manner, thereby causing delay in cell proliferation. However, for WB‐F344 cells, there is a paucity of such data, which are of substantial importance in understanding their radiation response. Here, the distribution of phases in the cell‐cycle and the proliferation ability of WB‐F344 cells are characterized at various time points after the cells have been irradiated with different doses of γ‐rays.
Methods
After WB‐F344 cells reached 100% confluence, they were trypsinized and suspended at 3.5 × 105 cells/ml in culture medium. Cells were irradiated in suspension with 137Cs γ‐rays at doses from 1–10 Gy. After irradiation, 1 × 105 cells were plated into 60 × 15‐mm culture dishes and incubated at 37°C, with 2% CO2 and 98% air. At 12, 24, 36, 48, and 60 h postirradiation, cells were harvested, counted, and subjected to flow cytometric cell‐cycle analysis.
Results
Growth curves of WB‐F344 cells irradiated with γ‐rays started to separate at 36 h postirradiation. By 60 h postirradiation, the growth curves for each of the 10 absorbed doses were distinctly separated. Drastic redistributions of control and irradiated cells within G0/G1‐, S‐, and G2/M‐phases of the cell cycle were observed during the first 36 h of cell growth. At each time point postirradiation, cell‐cycle phase profiles of irradiated cells were altered in a dose‐dependent manner. In general, there was a strong correlation between the percentage of G2/M‐phase cells and absorbed dose, with the exception of 24 h postirradiation. The percentage of G2/M‐phase cells increased as a function of time postirradiation, suggestive of delays in the passage of cells through the G2 cell‐cycle checkpoint.
Conclusions
This work provides a general description of cell cycle redistribution and repopulation kinetics of WB‐F344 cells at various times postirradiation of quiescent cells that were subsequently allowed to proliferate. In general, growth inhibition and delays in progression through G2/M‐phase correlated well with radiation dose. These data should be of considerable significance in the design of experiments that examine the radiation response of these cells. © 2004 Wiley‐Liss, Inc.