Characterization of cell-cycle progression and growth of WB-F344 normal rat liver epithelial cells following gamma-ray exposure.
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 gamma-rays.


METHODS
After WB-F344 cells reached 100% confluence, they were trypsinized and suspended at 3.5 x 10(5) cells/ml in culture medium. Cells were irradiated in suspension with (137)Cs gamma-rays at doses from 1-10 Gy. After irradiation, 1 x 10(5) cells were plated into 60 x 15-mm culture dishes and incubated at 37 degrees C, with 2% CO(2) 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 gamma-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 G(0)/G(1)-, S-, and G(2)/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 G(2)/M-phase cells and absorbed dose, with the exception of 24 h postirradiation. The percentage of G(2)/M-phase cells increased as a function of time postirradiation, suggestive of delays in the passage of cells through the G(2) 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 G(2)/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.
Gerashchenko
Bogdan I
BI
Department of Radiology, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, NJ 07103, USA.
Azzam
Edouard I
EI
Howell
Roger W
RW
D000818:Animals; D002453:Cell Cycle / Q000528:radiation effects*; D002455:Cell Division; D002460:Cell Line; D049109:Cell Proliferation / Q000528:radiation effects*; D002469:Cell Separation; D004247:DNA / Q000737:chemistry; D004307:Dose-Response Relationship, Radiation; D005434:Flow Cytometry; D016195:G2 Phase; D005720:Gamma Rays; D007091:Image Processing, Computer-Assisted; D051381:Rats; D011916:Rats, Inbred F344; D013997:Time Factors
D004247:DNA