Role of energy in cellular responses to heat.

We have examined the effect of heat on energy-generating processes and on parameters of bioenergetic status in animal cells. Heat inactivates several processes involved in uptake and metabolism of nutrients. In particular, insulin-stimulated hexose transport in HA-1 fibroblasts and electron transport in blowfly sarcosomes (Bowler, 1981) exhibit thermal sensitivities that reflect the vulnerability to heat of the whole cell or organism. These heat-induced lesions in energy production are not, however, reflected by parameters of energy status in most cells studied. In HA-1 fibroblasts, for instance, over 99% of cells are killed by 45 degrees C heat before a decrease is observed in any parameter of energy status. A general role for energy in cellular responses to heat thus seems unlikely, although the thermal responses of tissues in vivo may differ from those of cells in vitro.