Mechanism of alteration of poly(adenosine diphosphate-ribose) metabolism by hyperthermia

The effects of hyperthermia on adenine nucleotide metabolism including NAD and poly(ADP-ribose) have been studied in confluent cultures of C3H10T1/2 cells. Cells replated immediately following hyperthermic treatment showed only 9% survival relative to controls while after a 24-h recovery period at 37 degrees C survival was 87% of control. Hyperthermic treatment caused no detectable effect on total cellular levels of either NAD or ATP but produced a prolonged increase in cellular content of poly(ADP-ribose). Studies of the mechanism of this effect show that a major alteration of poly(ADP-ribose) metabolism caused by hyperthermia involves a decrease in the rate of turnover of polymers of ADP-ribose. Normal polymer turnover rates were restored during recovery at 37 degrees C even in the presence of cyclohexamide. The results argue that poly(ADP-ribose) glycohydrolase activity is reversibly altered by hyperthermia. Inhibition of poly(ADP-ribose) synthesis following hyperthermia delays recovery of normal rates of protein synthesis and recovery of the ability of the cells to plate and form colonies.