Investigation of adenylate energy charge, phosphorylation potential, and ATP concentration in cells stressed with starvation and heat.

We have attempted to determine the appropriate parameter of energy status associated with the survival of CHO fibroblasts under starvation conditions. Survival correlated well with adenylate energy charge (EC) but not so well with the phosphorylation potential or ATP concentration. Starved cells exhibited the capacity to resist (transiently) decreases in both EC and survival. A fall in EC was associated with decreased survival. Using this correlation, we subsequently investigated whether killing after thermal stress occurred by a mechanism analogous to starvation, perhaps due to inhibition of energy yielding pathways. This hypothesis proved to be false; over 99% of cells were killed before a decrease was observed in any of the parameters of energy status. Cells were, however, sensitized to heat under nutritionally deprived conditions, a finding which may be significant for tumor treatment by heat in vivo.