IS POLYAMINE DECREASE A COMMON FEATURE OF APOPTOSIS - EVIDENCE FROM GAMMA-RAYS-INDUCED AND HEAT-SHOCK-INDUCED CELL-DEATH

Here we report that in rat thymocytes undergoing apoptosis upon two di fferent stimuli, such as heat shock treatment and gamma irradiation, a n early mRNA accumulation of ornithine decarboxylase (ODC) - the rate- limiting enzyme of polyamine biosynthesis - was followed by a very mar ked increase in ODC activity (28-40 and 6-8-fold, respectively). Howev er, polyamine levels started to decrease before the appearance of DNA laddering, being putrescine and spermidine strongly diminished (8-12 h a), and spermine even depleted (12 hs). Taken together with our previo us data on another model of apoptosis, i.e., glucocorticoid-induced ce ll death (Desiderio et al., Cell Growth Differ. 6: 505-513, 1995), the se results suggest that an imbalance of polyamine metabolism. i.e., a strong activation of ODC and a paradoxical decrease of the intracellul ar polyamine content, might be a general feature of the apoptotic proc ess. (C) 1995 Academic Press, Inc.