THE polyamines spermine, spermidine and their precursor putrescine occur ubiquitously and in high concentrations in animals and plants1. Increased polyamine synthesis in animal cells and bacteria precedes or coincides with enhanced RNA formation, especially during growth stimulation, suggesting a close relationship2. Ornithine decarboxylase (ODC), a rate-limiting enzyme in polyamine synthesis, has an extremely short half life3. The early, large increase in its activity in all cases of rapid tissue growth examined suggests that the formation of its product, putrescine, triggers early enhancement of RNA synthesis during cellular growth. A critical test of this concept would be to block net putrescine and (or) polyamine synthesis selectively and determine whether nucleic acid synthesis is altered. Such a test might assess the role of putrescine as a potential modulator of growth in normal and neoplastic tissue.
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