Effect of hyperthermia on spermidine/spermine N1-acetyltransferase activity in Ehrlich ascites cells

When Ehrlich ascites tumor cells were incubated at 42 degrees C, the activity of spermidine/spermine N1-acetyltransferase, a rate-limiting enzyme of polyamine biodegradation, decreased to 20% of the control level within 1 hr. Protein synthesis, judged from the incorporation of [3H]leucine into the acid-insoluble fraction, was less affected by heat exposure. The decrease in the enzyme activity caused by heat treatment could be reversed by switching the incubation temperature back to 37 degrees C. The reversion of enzyme activity was suppressed by cycloheximide but not by actinomycin D.