Ornithine decarboxylase induction and nucleolar RNA synthesis in Friend leukemia cells

The induction of ornithine decarboxylase and the stimulation of nucleolar RNA synthesis following dilution of stationary phase Friend Leukemia Cells into fresh medium were studied. Ornithine decarboxylase activity and the rate of nucleolar RNA synthesis reached maximum values within 4 hours after dilution, with ornithine decarboxylase levels increasing 10–20 fold and nucleolar RNA synthesis increasing by about 60% during this period. 0.5 mM putrescine effectively inhibited the rise in ornithine decarboxylase following cell transfer, but did not prevent increases in the rate of nucleolar RNA synthesis.