Control by hyperthermia of ornithine decarboxylase in Ehrlich ascites tumor cells.

The effect of hyperthermia on the activity and the messenger RNA levels of ornithine decarboxylase (ODC), which has a rapid rate of turnover in cultured cells, was studied in Ehrlich ascites tumor cells. When the cells were incubated at 42 degrees C, elevation of ODC activity by a change of the medium was prevented. Total RNA was isolated from cells treated at 37 degrees C or 42 degrees C, and the relative abundance of the ODC mRNA was measured by Northern blot analysis. These levels in heat-treated cells were comparable to those in control cells. Inhibition by hyperthermia was reversible. The recovery was suppressed by cycloheximide but not by actinomycin D. In hyperthermic-treated cells, the biological half-life of ODC was 14 min, which was the same time as for cells cultured at 37 degrees C. These results suggest that hyperthermic treatment of Ehrlich ascites tumor cells suppressed ODC induction during translation, not during transcription or after translation.