GROWTH AND SURVIVAL OF MAMMALIAN CELLS UNDER CONTINUOUS THERMAL STRESS

Pig kidney cells were cultivated for extended periods at supranormal temperatures to isolate variants with altered response to thermal stress. Sublines of cells were eventually obtained which showed increased survival at 42.5 °C. The variant property was stable in cells subcultivated at 37 °C, but could not be enhanced by further heat treatments. This strain was compared with three heat-resistant lines obtained previously by acute heat shock at 47 °C. In growth experiments at 42.5 °C, the latter were no more resistant than cells previously not exposed to supranormal temperatures. Correspondingly, the variant subline with increased survival at 42.5 °C proved to be as sensitive as control cells when exposed for short intervals at 47 °C. These results suggest that heat resistance is mediated by separate mechanisms in acute heat shock and prolonged thermal stress respectively. © 1969.