In vitro holding and PLD repair. I. On the contribution of mitotic non-quiescence in plateau-phase Chinese hamster V79 cells.
The Stationary or Plateau-Phase of commonly used rodent cell lines like the V79 are often assumed to be quiescent (non-mitotic). An analysis of cell turnover in V79 plateau-phase cultures through BrUdR-incorporation combined with FUdR-block and light exposure (S-phase cytocide) revealed such cultures to be in a state of kinetic equilibrium. Even when the state of maximal permissible density was acquired, at least 50% of the population of cells were cycling within the time for one population doubling. Attempts at holding the cells from cycling (through nutrient-depletion and serum-privation) were unsuccessful, although the turnover-rate was reduced. Our assays for X-irradiated clonogenic survivors after attempted holding combined with delayed plating (DP) showed differences in the survival curves for exponentially growing and confluent cultures. Elimination of cycling cells by S-phase cytocide removed these differences. Since a significant fraction of plateau-phase cells are not mitotically quiescent (Q), one must eliminate the proliferating (P) fraction if one wishes to examine the PLDR of the Q cells. For V79 cells, removal of the P cells eliminates the higher survival (usually interpreted as Q cell PLDR) of plateau-phase cells.
Stevenson
A F
AF
Department of Radiation Oncology, SUNY, Health Science Center, Brooklyn 11203.
Lange
C S
CS
D000818:Animals; D001973:Bromodeoxyuridine / Q000494:pharmacology; D002453:Cell Cycle; D002470:Cell Survival; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D006224:Cricetinae; D004249:DNA Damage; D005467:Floxuridine / Q000494:pharmacology; D008854:Microscopy, Electron; D008938:Mitosis / Q000528:radiation effects*
D005467:Floxuridine; D001973:Bromodeoxyuridine