Various aspects of growth and radiation survival characteristics of the V79-171B Chinese hamster cell line have been studied during conventional growth on petri dishes. As cells aged after subculture, the cell cycle elongated progressively due primarily to the lengthening of G1 phase. Plateau phase cultures were partially synchronous in a <tex-math>${\rm G}_{1}\text{-like}$</tex-math> stage of the cell cycle, but had a radiation survival curve characterized by an extrapolation number 15- to 20-fold higher than that of early G1 phase cells from exponential cultures, and 3- to 4-fold larger than that of asynchronous, exponentially growing cells. No variations in radiosensitivity (D0) were observed. The similarity of these results to those obtained when this cell line was grown under conditions of extensive intercellular contact as multicellular spheroids suggested that intercellular contact may have been responsible for the enhanced survival observed. Despite this enhanced capacity for accumulation of sublethal radiation damage, the relative ability of plateau phase cells to repair sublethal damage was not significantly larger than that of exponentially growing cells. Potentially lethal radiation damage was not additionally repaired under numerous suboptimal growth conditions studied.

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