Control by hyperthermia of ornithine decar☐ylase in Ehrlich ascites tumor cells

Abstract

The effect of hyperthermia on the activity and the messenger RNA levels of ornithine decar☐ylase (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°C, elevation of ODC activity by a change of the medium was prevented. Total RNA was isolated from cells treated at 37°C or 42°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°C. These results suggest that hyperthermic treatment of Ehrlich ascites tumor cells suppressed ODC induction during translation, not during transcription or after translation.