DNA degradation in chinese hamster ovary cells after exposure to hyperthermia.

Chinese hamster ovary cells grown in suspension showed a progressive reduction in the size of their nuclear DNA to 50 to 60S fragments after hyperthermia (43-48 degrees). This DNA degradation was not a homogeneous response but was observed only in cells incapable of attaching to a substratum after acute heating. The DNA degradation was associated with the inability of cells to exclude the vital stain, trypan blue. The degradation process appeared to be a result of nucleolytic enzyme digestion which accompanies cell necrosis. A similar phenomenon was observed in heated monolayer cells but only after significantly greater time-temperature exposures. Our results show that cellular subpopulations can be separated after hyperthermia and that these subpopulations are biochemically distinct and characterized by different viability.