Nms. Reddy et al., NUTRIENT DILUTION BEFORE AND AFTER X-IRRADIATION INCREASES THE RADIORESISTANCE OF LOG-PHASE AND PLATEAU-PHASE CHINESE-HAMSTER V79 CELLS, Radiation research, 147(1), 1997, pp. 115-118
Previous observations have shown that cells cultured in standard growt
h medium (100%) demonstrated similarly enhanced survival when incubate
d postirradiation either in non-growth-promoting conditioned medium or
in growth-promoting 40% growth medium (Reddy and Lange, Radial. Res.
119, 338-347, 1989). From these results, it was suggested that nutrien
t dilution altered radiosensitivity by a mechanism independent of prog
ression of cells through the cell cycle. In this study, we have examin
ed the effects on radiosensitivity of incubation in 40% growth medium
prior to irradiation on both log- and plateau-phase Chinese hamster V7
9 cells and the effects on the distribution of cells in the cell cycle
of incubation in 40% or 100% growth medium before and after irradiati
on. Radioresistance increased by a factor of 1.5-1.6 compared to 100%
growth medium for both log-phase and plateau-phase cells cultured in 4
0% growth medium prior to X irradiation and incubated in either 40% gr
owth medium or conditioned medium after X irradiation. The cell cycle
distributions of log-phase cells in 100% and 40% growth medium before
irradiation were identical. The change in cell cycle distribution indu
ced by 10 Gy did not differ among log-phase cells incubated for 3 h po
stirradiation in 100% growth medium, 40% growth medium or conditioned
medium. These results, in addition to supporting our previous conclusi
ons, demonstrate that culturing prior to irradiation in 40% growth med
ium alone increases cell survival and that incubation in 40% growth me
dium before and after irradiation maximizes the survival of V79 cells.
(C) 1997 by Radiation Research Society